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impala/docs/topics/impala_string_functions.xml
Alex Rodoni e8ee827a6d [DOCS] Built-in Functions doc format Changes 
- The function titles were changed to upper case.
- The function titles no longer use <codeph>. <codeph> font appears
smaller than the <p> font.
- Return type were changed to upper case data types.
- Minor typos were fixed, such as extra commas and periods in titles.
- The indexterm dita elememts were removed. Indexterm was incomplete
and WIP. No plan to go ahead and implement it, so removed.

Change-Id: I797532463da8d29fe5bc7543cfdfb5b2b82db197
Reviewed-on: http://gerrit.cloudera.org:8080/11619
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Reviewed-by: Michael Brown <mikeb@cloudera.com>
2018-10-10 18:18:09 +00:00

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<?xml version="1.0" encoding="UTF-8"?>
<!--
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specific language governing permissions and limitations
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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="string_functions">
<title>Impala String Functions</title>
<titlealts audience="PDF">
<navtitle>String Functions</navtitle>
</titlealts>
<prolog>
<metadata>
<data name="Category" value="Impala"/>
<data name="Category" value="Impala Functions"/>
<data name="Category" value="SQL"/>
<data name="Category" value="Data Analysts"/>
<data name="Category" value="Developers"/>
<data name="Category" value="Querying"/>
</metadata>
</prolog>
<conbody>
<p rev="2.0.0">
String functions are classified as those primarily accepting or returning
<codeph>STRING</codeph>, <codeph>VARCHAR</codeph>, or <codeph>CHAR</codeph> data types,
for example to measure the length of a string or concatenate two strings together.
<ul>
<li>
All the functions that accept <codeph>STRING</codeph> arguments also accept the
<codeph>VARCHAR</codeph> and <codeph>CHAR</codeph> types introduced in Impala 2.0.
</li>
<li>
Whenever <codeph>VARCHAR</codeph> or <codeph>CHAR</codeph> values are passed to a
function that returns a string value, the return type is normalized to
<codeph>STRING</codeph>. For example, a call to <codeph>CONCAT()</codeph> with a mix
of <codeph>STRING</codeph>, <codeph>VARCHAR</codeph>, and <codeph>CHAR</codeph>
arguments produces a <codeph>STRING</codeph> result.
</li>
</ul>
</p>
<p conref="../shared/impala_common.xml#common/related_info"/>
<p>
The string functions operate mainly on these data types:
<xref href="impala_string.xml#string"/>, <xref href="impala_varchar.xml#varchar"/>, and
<xref href="impala_char.xml#char"/>.
</p>
<p>
<b>Function reference:</b>
</p>
<p>
Impala supports the following string functions:
</p>
<ul>
<li>
<xref href="#string_functions/ascii">ASCII</xref>
</li>
<li>
<xref href="#string_functions/base64decode">BASE64DECODE</xref>
</li>
<li>
<xref href="#string_functions/base64encode">BASE64ENCODE</xref>
</li>
<li>
<xref href="#string_functions/btrim">BTRIM</xref>
</li>
<li>
<xref href="#string_functions/char_length">CHAR_LENGTH</xref>
</li>
<li>
<xref href="#string_functions/chr">CHR</xref>
</li>
<li>
<xref href="#string_functions/concat">CONCAT</xref>
</li>
<li>
<xref href="#string_functions/concat_ws">CONCAT_WS</xref>
</li>
<li>
<xref href="#string_functions/find_in_set">FIND_IN_SET</xref>
</li>
<li>
<xref href="#string_functions/group_concat">GROUP_CONCAT</xref>
</li>
<li>
<xref href="#string_functions/initcap">INITCAP</xref>
</li>
<li>
<xref href="#string_functions/instr">INSTR</xref>
</li>
<li>
<xref href="#string_functions/left">LEFT</xref>
</li>
<li>
<xref href="#string_functions/length">LENGTH</xref>
</li>
<li>
<xref href="#string_functions/locate">LOCATE</xref>
</li>
<li>
<xref href="#string_functions/lower">LOWER, LCASE</xref>
</li>
<li>
<xref href="#string_functions/lpad">LPAD</xref>
</li>
<li>
<xref href="#string_functions/ltrim">LTRI </xref>
</li>
<li>
<xref href="#string_functions/parse_url">PARSE_URL</xref>
</li>
<li>
<xref href="#string_functions/regexp_escape">REGEXP_ESCAPE</xref>
</li>
<li>
<xref href="#string_functions/regexp_extract">REGEXP_EXTRACT</xref>
</li>
<li>
<xref href="#string_functions/regexp_like">REGEXP_LIKE</xref>
</li>
<li>
<xref href="#string_functions/regexp_replace">REGEXP_REPLACE</xref>
</li>
<li>
<xref href="#string_functions/repeat">REPEAT</xref>
</li>
<li>
<xref href="#string_functions/replace">REPLACE</xref>
</li>
<li>
<xref href="#string_functions/reverse">REVERSE</xref>
</li>
<li>
<xref href="#string_functions/right">RIGHT</xref>
</li>
<li>
<xref href="#string_functions/rpad">RPAD</xref>
</li>
<li>
<xref href="#string_functions/rtrim">RTRIM</xref>
</li>
<li>
<xref href="#string_functions/space">SPACE</xref>
</li>
<li>
<xref href="#string_functions/split_part">SPLIT_PART</xref>
</li>
<li>
<xref href="#string_functions/strleft">STRLEFT</xref>
</li>
<li>
<xref href="#string_functions/strright">STRRIGHT</xref>
</li>
<li>
<xref href="#string_functions/substr">SUBSTR, SUBSTRING</xref>
</li>
<li>
<xref href="#string_functions/translate">TRANSLATE</xref>
</li>
<li>
<xref href="#string_functions/trim">TRIM</xref>
</li>
<li>
<xref href="#string_functions/upper">UPPER, UCASE</xref>
</li>
</ul>
<dl>
<dlentry id="ascii">
<dt>
ASCII(STRING str)
</dt>
<dd>
<b>Purpose:</b> Returns the numeric ASCII code of the first character of the argument.
<p>
<b>Return type:</b> <codeph>INT</codeph>
</p>
</dd>
</dlentry>
<dlentry id="base64decode" rev="2.6.0 IMPALA-2107">
<dt>
BASE64DECODE(STRING str)
</dt>
<dd>
<b>Purpose:</b>
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
<p>
For general information about Base64 encoding, see
<xref
keyref="base64"/>.
</p>
<p conref="../shared/impala_common.xml#common/base64_use_cases"/>
<p conref="../shared/impala_common.xml#common/base64_charset"/>
<p conref="../shared/impala_common.xml#common/base64_alignment"/>
<p conref="../shared/impala_common.xml#common/base64_error_handling"/>
<p conref="../shared/impala_common.xml#common/example_blurb"/>
<p conref="../shared/impala_common.xml#common/base64_examples"/>
</dd>
</dlentry>
<dlentry id="base64encode" rev="2.6.0 IMPALA-2107">
<dt>
BASE64ENCODE(STRING str)
</dt>
<dd>
<b>Purpose:</b>
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
<p>
For general information about Base64 encoding, see
<xref
keyref="base64"/>.
</p>
<p conref="../shared/impala_common.xml#common/base64_use_cases"/>
<p conref="../shared/impala_common.xml#common/base64_charset"/>
<p conref="../shared/impala_common.xml#common/base64_alignment"/>
<p conref="../shared/impala_common.xml#common/example_blurb"/>
<p conref="../shared/impala_common.xml#common/base64_examples"/>
</dd>
</dlentry>
<dlentry rev="2.3.0" id="btrim">
<dt>
BTRIM(STRING a), BTRIM(STRING a, STRING chars_to_trim)
</dt>
<dd>
<b>Purpose:</b> Removes all instances of one or more characters from the start and end
of a <codeph>STRING</codeph> value. By default, removes only spaces. If a
non-<codeph>NULL</codeph> optional second argument is specified, the function removes
all occurrences of characters in that second argument from the beginning and end of
the string.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p conref="../shared/impala_common.xml#common/added_in_230"/>
<p conref="../shared/impala_common.xml#common/example_blurb"/>
<p>
The following examples show the default <codeph>BTRIM()</codeph> behavior, and what
changes when you specify the optional second argument. All the examples bracket the
output value with <codeph>[ ]</codeph> so that you can see any leading or trailing
spaces in the <codeph>BTRIM()</codeph> result. By default, the function removes and
number of both leading and trailing spaces. When the second argument is specified,
any number of occurrences of any character in the second argument are removed from
the start and end of the input string; in this case, spaces are not removed (unless
they are part of the second argument) and any instances of the characters are not
removed if they do not come right at the beginning or end of the string.
</p>
<codeblock>-- Remove multiple spaces before and one space after.
select concat('[',btrim(' hello '),']');
+---------------------------------------+
| concat('[', btrim(' hello '), ']') |
+---------------------------------------+
| [hello] |
+---------------------------------------+
-- Remove any instances of x or y or z at beginning or end. Leave spaces alone.
select concat('[',btrim('xy hello zyzzxx','xyz'),']');
+------------------------------------------------------+
| concat('[', btrim('xy hello zyzzxx', 'xyz'), ']') |
+------------------------------------------------------+
| [ hello ] |
+------------------------------------------------------+
-- Remove any instances of x or y or z at beginning or end.
-- Leave x, y, z alone in the middle of the string.
select concat('[',btrim('xyhelxyzlozyzzxx','xyz'),']');
+----------------------------------------------------+
| concat('[', btrim('xyhelxyzlozyzzxx', 'xyz'), ']') |
+----------------------------------------------------+
| [helxyzlo] |
+----------------------------------------------------+
</codeblock>
</dd>
</dlentry>
<dlentry rev="1.3.0" id="char_length">
<dt>
CHAR_LENGTH(STRING a), CHARACTER_LENGTH(STRING a)
</dt>
<dd rev="IMPALA-6391 IMPALA-2172">
<b>Purpose:</b> Returns the length in characters of the argument string, including any
trailing spaces that pad a <codeph>CHAR</codeph> value.
<p>
<b>Return type:</b> <codeph>INT</codeph>
</p>
<p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
<p>
When applied to a <codeph>STRING</codeph> value, it returns the same result as the
<codeph>length()</codeph> function. When applied to a <codeph>CHAR</codeph> value,
it might return a larger value than <codeph>length()</codeph> does, to account for
trailing spaces in the <codeph>CHAR</codeph>.
</p>
<p conref="../shared/impala_common.xml#common/example_blurb"/>
<p conref="../shared/impala_common.xml#common/length_demo"/>
</dd>
</dlentry>
<dlentry rev="2.3.0" id="chr">
<dt>
CHR(INT character_code)
</dt>
<dd>
<b>Purpose:</b> Returns a character specified by a decimal code point value. The
interpretation and display of the resulting character depends on your system locale.
Because consistent processing of Impala string values is only guaranteed for values
within the ASCII range, only use this function for values corresponding to ASCII
characters. In particular, parameter values greater than 255 return an empty string.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p>
<b>Usage notes:</b> Can be used as the inverse of the <codeph>ascii()</codeph>
function, which converts a character to its numeric ASCII code.
</p>
<p conref="../shared/impala_common.xml#common/added_in_230"/>
<p conref="../shared/impala_common.xml#common/example_blurb"/>
<codeblock>SELECT chr(65);
+---------+
| chr(65) |
+---------+
| A |
+---------+
SELECT chr(97);
+---------+
| chr(97) |
+---------+
| a |
+---------+
</codeblock>
</dd>
</dlentry>
<dlentry id="concat">
<dt>
CONCAT(STRING a, STRING b...)
</dt>
<dd>
<b>Purpose:</b> Returns a single string representing all the argument values joined
together.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p conref="../shared/impala_common.xml#common/concat_blurb"/>
</dd>
</dlentry>
<dlentry id="concat_ws">
<dt>
CONCAT_WS(STRING sep, STRING a, STRING b...)
</dt>
<dd>
<b>Purpose:</b> Returns a single string representing the second and following argument
values joined together, delimited by a specified separator.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p conref="../shared/impala_common.xml#common/concat_blurb"/>
</dd>
</dlentry>
<dlentry id="find_in_set">
<dt>
FIND_IN_SEt(STRING str, STRING strList)
</dt>
<dd>
<b>Purpose:</b> Returns the position (starting from 1) of the first occurrence of a
specified string within a comma-separated string. Returns <codeph>NULL</codeph> if
either argument is <codeph>NULL</codeph>, 0 if the search string is not found, or 0 if
the search string contains a comma.
<p>
<b>Return type:</b> <codeph>INT</codeph>
</p>
</dd>
</dlentry>
<dlentry rev="1.2" id="group_concat">
<dt>
GROUP_CONCAT(STRING s [, STRING sep])
</dt>
<dd>
<b>Purpose:</b> Returns a single string representing the argument value concatenated
together for each row of the result set. If the optional separator string is
specified, the separator is added between each pair of concatenated values.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p conref="../shared/impala_common.xml#common/concat_blurb"/>
<p>
By default, returns a single string covering the whole result set. To include other
columns or values in the result set, or to produce multiple concatenated strings for
subsets of rows, include a <codeph>GROUP BY</codeph> clause in the query.
</p>
<p>
Strictly speaking, <codeph>GROUP_CONCAT()</codeph> is an aggregate function, not a
scalar function like the others in this list. For additional details and examples,
see <xref
href="impala_group_concat.xml#group_concat"/>.
</p>
</dd>
</dlentry>
<dlentry rev="1.2" id="initcap">
<dt>
INITCAP(STRING str)
</dt>
<dd>
<b>Purpose:</b> Returns the input string with the first letter capitalized.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
</dd>
</dlentry>
<dlentry id="instr">
<dt>
INSTR(STRING str, STRING substr <ph rev="IMPALA-3973">[, BIGINT position [, BIGINT
occurrence ] ]</ph>)
</dt>
<dd>
<b>Purpose:</b> Returns the position (starting from 1) of the first occurrence of a
substring within a longer string.
<p>
<b>Return type:</b> <codeph>INT</codeph>
</p>
<p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
<p>
If the substring is not present in the string, the function returns 0:
</p>
<codeblock rev="IMPALA-3973 2.8.0">
select instr('foo bar bletch', 'z');
+------------------------------+
| instr('foo bar bletch', 'z') |
+------------------------------+
| 0 |
+------------------------------+
</codeblock>
<p rev="IMPALA-3973 2.8.0">
The optional third and fourth arguments let you find instances of the substring
other than the first instance starting from the left:
</p>
<ul>
<li>
<p>
The third argument lets you specify a starting point within the string other
than 1:
</p>
<codeblock>
-- Restricting the search to positions 7..end,
-- the first occurrence of 'b' is at position 9.
select instr('foo bar bletch', 'b', 7);
+---------------------------------+
| instr('foo bar bletch', 'b', 7) |
+---------------------------------+
| 9 |
+---------------------------------+
-- If there are no more occurrences after the
-- specified position, the result is 0.
select instr('foo bar bletch', 'b', 10);
+----------------------------------+
| instr('foo bar bletch', 'b', 10) |
+----------------------------------+
| 0 |
+----------------------------------+
</codeblock>
<p>
If the third argument is negative, the search works right-to-left starting that
many characters from the right. The return value still represents the position
starting from the left side of the string.
</p>
<codeblock rev="IMPALA-3973 2.8.0">
-- Scanning right to left, the first occurrence of 'o'
-- is at position 8. (8th character from the left.)
select instr('hello world','o',-1);
+-------------------------------+
| instr('hello world', 'o', -1) |
+-------------------------------+
| 8 |
+-------------------------------+
-- Scanning right to left, starting from the 6th character
-- from the right, the first occurrence of 'o' is at
-- position 5 (5th character from the left).
select instr('hello world','o',-6);
+-------------------------------+
| instr('hello world', 'o', -6) |
+-------------------------------+
| 5 |
+-------------------------------+
-- If there are no more occurrences after the
-- specified position, the result is 0.
select instr('hello world','o',-10);
+--------------------------------+
| instr('hello world', 'o', -10) |
+--------------------------------+
| 0 |
+--------------------------------+
</codeblock>
</li>
<li>
<p>
The fourth argument lets you specify an occurrence other than the first:
</p>
<codeblock rev="IMPALA-3973 2.8.0">
-- 2nd occurrence of 'b' is at position 9.
select instr('foo bar bletch', 'b', 1, 2);
+------------------------------------+
| instr('foo bar bletch', 'b', 1, 2) |
+------------------------------------+
| 9 |
+------------------------------------+
-- Negative position argument means scan right-to-left.
-- This example finds second instance of 'b' from the right.
select instr('foo bar bletch', 'b', -1, 2);
+-------------------------------------+
| instr('foo bar bletch', 'b', -1, 2) |
+-------------------------------------+
| 5 |
+-------------------------------------+
</codeblock>
<p>
If the fourth argument is greater than the number of matching occurrences, the
function returns 0:
</p>
<codeblock>
-- There is no 3rd occurrence within the string.
select instr('foo bar bletch', 'b', 1, 3);
+------------------------------------+
| instr('foo bar bletch', 'b', 1, 3) |
+------------------------------------+
| 0 |
+------------------------------------+
-- There is not even 1 occurrence when scanning
-- the string starting at position 10.
select instr('foo bar bletch', 'b', 10, 1);
+-------------------------------------+
| instr('foo bar bletch', 'b', 10, 1) |
+-------------------------------------+
| 0 |
+-------------------------------------+
</codeblock>
<p>
The fourth argument cannot be negative or zero. A non-positive value for this
argument causes an error:
</p>
<codeblock>
select instr('foo bar bletch', 'b', 1, 0);
ERROR: UDF ERROR: Invalid occurrence parameter to instr function: 0
select instr('aaaaaaaaa','aa', 1, -1);
ERROR: UDF ERROR: Invalid occurrence parameter to instr function: -1
</codeblock>
</li>
<li>
<p>
If either of the optional arguments is <codeph>NULL</codeph>, the function also
returns <codeph>NULL</codeph>:
</p>
<codeblock>
select instr('foo bar bletch', 'b', null);
+------------------------------------+
| instr('foo bar bletch', 'b', null) |
+------------------------------------+
| NULL |
+------------------------------------+
select instr('foo bar bletch', 'b', 1, null);
+---------------------------------------+
| instr('foo bar bletch', 'b', 1, null) |
+---------------------------------------+
| NULL |
+---------------------------------------+
</codeblock>
</li>
</ul>
</dd>
</dlentry>
<dlentry id="left">
<dt>
LEFT(STRING a, INT num_chars)
</dt>
<dd>
See the <codeph>STRLEFT()</codeph> function.
</dd>
</dlentry>
<dlentry id="length">
<dt>
LENGTH(STRING a)
</dt>
<dd rev="IMPALA-6391 IMPALA-2172">
<b>Purpose:</b> Returns the length in characters of the argument string, ignoring any
trailing spaces in <codeph>CHAR</codeph> values.
<p>
<b>Return type:</b> <codeph>INT</codeph>
</p>
<p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
<p>
When applied to a <codeph>STRING</codeph> value, it returns the same result as the
<codeph>CHAR_LENGTH()</codeph> function. When applied to a <codeph>CHAR</codeph>
value, it might return a smaller value than <codeph>CHAR_LENGTH()</codeph> does,
because <codeph>LENGTH()</codeph> ignores any trailing spaces in the
<codeph>CHAR</codeph>.
</p>
<note>
Because the behavior of <codeph>LENGTH()</codeph> with <codeph>CHAR</codeph> values
containing trailing spaces is not standardized across the industry, when porting
code from other database systems, evaluate the behavior of <codeph>LENGTH()</codeph>
on the source system and switch to <codeph>CHAR_LENGTH()</codeph> for Impala if
necessary.
</note>
<p conref="../shared/impala_common.xml#common/example_blurb"/>
<p conref="../shared/impala_common.xml#common/length_demo"/>
</dd>
</dlentry>
<dlentry id="locate">
<dt>
LOCATE(STRING substr, STRING str[, INT pos])
</dt>
<dd>
<b>Purpose:</b> Returns the position (starting from 1) of the first occurrence of a
substring within a longer string, optionally after a particular position.
<p>
<b>Return type:</b> <codeph>INT</codeph>
</p>
</dd>
</dlentry>
<dlentry id="lower">
<dt>
LOWER(STRING a), <ph id="lcase">LCASE(STRING a)</ph>
</dt>
<dd>
<b>Purpose:</b> Returns the argument string converted to all-lowercase.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
<p
conref="../shared/impala_common.xml#common/case_insensitive_comparisons_tip"
/>
</dd>
</dlentry>
<dlentry id="lpad">
<dt>
LPAD(STRING str, INT len, STRING pad)
</dt>
<dd>
<b>Purpose:</b> Returns a string of a specified length, based on the first argument
string. If the specified string is too short, it is padded on the left with a
repeating sequence of the characters from the pad string. If the specified string is
too long, it is truncated on the right.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
</dd>
</dlentry>
<dlentry id="ltrim">
<dt>
LTRIM(STRING a [, STRING chars_to_trim])
</dt>
<dd>
<b>Purpose:</b> Returns the argument string with all occurrences of characters
specified by the second argument removed from the left side. Removes spaces if the
second argument is not specified.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
</dd>
</dlentry>
<dlentry id="parse_url">
<dt>
PARSE_URL(STRING urlString, STRING partToExtract [, STRING keyToExtract])
</dt>
<dd>
<indexterm audience="hidden">parse_url() function</indexterm>
<b>Purpose:</b> Returns the portion of a URL corresponding to a specified part. The
part argument can be <codeph>'PROTOCOL'</codeph>, <codeph>'HOST'</codeph>,
<codeph>'PATH'</codeph>, <codeph>'REF'</codeph>, <codeph>'AUTHORITY'</codeph>,
<codeph>'FILE'</codeph>, <codeph>'USERINFO'</codeph>, or <codeph>'QUERY'</codeph>.
Uppercase is required for these literal values. When requesting the
<codeph>QUERY</codeph> portion of the URL, you can optionally specify a key to
retrieve just the associated value from the key-value pairs in the query string.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p>
<b>Usage notes:</b> This function is important for the traditional Hadoop use case
of interpreting web logs. For example, if the web traffic data features raw URLs not
divided into separate table columns, you can count visitors to a particular page by
extracting the <codeph>'PATH'</codeph> or <codeph>'FILE'</codeph> field, or analyze
search terms by extracting the corresponding key from the <codeph>'QUERY'</codeph>
field.
</p>
</dd>
</dlentry>
<dlentry rev="3.0" id="regexp_escape">
<dt>
REGEXP_ESCAPE(STRING source)
</dt>
<dd>
<b>Purpose:</b> The <codeph>REGEXP_ESCAPE()</codeph> function returns a string escaped
for the special character in RE2 library so that the special characters are
interpreted literally rather than as special characters. The following special
characters are escaped by the function:
<codeblock><![CDATA[.\+*?[^]$(){}=!<>|:-]]></codeblock>
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p conref="../shared/impala_common.xml#common/regexp_re2"/>
<p conref="../shared/impala_common.xml#common/regexp_re2_warning"/>
<p conref="../shared/impala_common.xml#common/regexp_escapes"/>
<p conref="../shared/impala_common.xml#common/example_blurb"/>
<p>
This example shows escaping one of special characters in RE2.
</p>
<codeblock>
+------------------------------------------------------+
| regexp_escape('Hello.world') |
+------------------------------------------------------+
| Hello\.world |
+------------------------------------------------------+
</codeblock>
<p>
This example shows escaping all the special characters in RE2.
</p>
<codeblock><![CDATA[
+------------------------------------------------------------+
| regexp_escape('a.b\\c+d*e?f[g]h$i(j)k{l}m=n!o<p>q|r:s-t') |
+------------------------------------------------------------+
| a\.b\\c\+d\*e\?f\[g\]h\$i\(j\)k\{l\}m\=n\!o\<p\>q\|r\:s\-t |
+------------------------------------------------------------+
]]>
</codeblock>
</dd>
</dlentry>
<dlentry id="regexp_extract">
<dt>
REGEXP_EXTRACT(STRING subject, STRING pattern, INT index)
</dt>
<dd>
<b>Purpose:</b> Returns the specified () group from a string based on a regular
expression pattern. Group 0 refers to the entire extracted string, while group 1, 2,
and so on refers to the first, second, and so on <codeph>(...)</codeph> portion.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p conref="../shared/impala_common.xml#common/regexp_re2"/>
<p conref="../shared/impala_common.xml#common/regexp_re2_warning"/>
<p conref="../shared/impala_common.xml#common/regexp_escapes"/>
<p conref="../shared/impala_common.xml#common/example_blurb"/>
<p>
This example shows how group 0 matches the full pattern string, including the
portion outside any <codeph>()</codeph> group:
</p>
<codeblock>[localhost:21000] &gt; select regexp_extract('abcdef123ghi456jkl','.*?(\\d+)',0);
+------------------------------------------------------+
| regexp_extract('abcdef123ghi456jkl', '.*?(\\d+)', 0) |
+------------------------------------------------------+
| abcdef123ghi456 |
+------------------------------------------------------+
Returned 1 row(s) in 0.11s</codeblock>
<p>
This example shows how group 1 matches just the contents inside the first
<codeph>()</codeph> group in the pattern string:
</p>
<codeblock>[localhost:21000] &gt; select regexp_extract('abcdef123ghi456jkl','.*?(\\d+)',1);
+------------------------------------------------------+
| regexp_extract('abcdef123ghi456jkl', '.*?(\\d+)', 1) |
+------------------------------------------------------+
| 456 |
+------------------------------------------------------+
Returned 1 row(s) in 0.11s</codeblock>
<p rev="2.0.0">
Unlike in earlier Impala releases, the regular expression library used in Impala 2.0
and later supports the <codeph>.*?</codeph> idiom for non-greedy matches. This
example shows how a pattern string starting with <codeph>.*?</codeph> matches the
shortest possible portion of the source string, returning the rightmost set of
lowercase letters. A pattern string both starting and ending with
<codeph>.*?</codeph> finds two potential matches of equal length, and returns the
first one found (the leftmost set of lowercase letters).
</p>
<codeblock>[localhost:21000] &gt; select regexp_extract('AbcdBCdefGHI','.*?([[:lower:]]+)',1);
+--------------------------------------------------------+
| regexp_extract('abcdbcdefghi', '.*?([[:lower:]]+)', 1) |
+--------------------------------------------------------+
| def |
+--------------------------------------------------------+
[localhost:21000] &gt; select regexp_extract('AbcdBCdefGHI','.*?([[:lower:]]+).*?',1);
+-----------------------------------------------------------+
| regexp_extract('abcdbcdefghi', '.*?([[:lower:]]+).*?', 1) |
+-----------------------------------------------------------+
| bcd |
+-----------------------------------------------------------+
</codeblock>
</dd>
</dlentry>
<dlentry rev="2.3.0" id="regexp_like">
<dt>
REGEXP_LIKE(STRING source, STRING pattern[, STRING options])
</dt>
<dd>
<b>Purpose:</b> Returns <codeph>true</codeph> or <codeph>false</codeph> to indicate
whether the source string contains anywhere inside it the regular expression given by
the pattern. The optional third argument consists of letter flags that change how the
match is performed, such as <codeph>i</codeph> for case-insensitive matching.
<p
conref="../shared/impala_common.xml#common/syntax_blurb"/>
<p>
The flags that you can include in the optional third argument are:
</p>
<ul>
<li>
<codeph>c</codeph>: Case-sensitive matching (the default).
</li>
<li>
<codeph>i</codeph>: Case-insensitive matching. If multiple instances of
<codeph>c</codeph> and <codeph>i</codeph> are included in the third argument, the
last such option takes precedence.
</li>
<li>
<codeph>m</codeph>: Multi-line matching. The <codeph>^</codeph> and
<codeph>$</codeph> operators match the start or end of any line within the source
string, not the start and end of the entire string.
</li>
<li>
<codeph>n</codeph>: Newline matching. The <codeph>.</codeph> operator can match
the newline character. A repetition operator such as <codeph>.*</codeph> can match
a portion of the source string that spans multiple lines.
</li>
</ul>
<p>
<b>Return type:</b> <codeph>BOOLEAN</codeph>
</p>
<p conref="../shared/impala_common.xml#common/regexp_re2"/>
<p conref="../shared/impala_common.xml#common/regexp_re2_warning"/>
<p conref="../shared/impala_common.xml#common/regexp_escapes"/>
<p conref="../shared/impala_common.xml#common/example_blurb"/>
<p>
This example shows how <codeph>regexp_like()</codeph> can test for the existence of
various kinds of regular expression patterns within a source string:
</p>
<codeblock><![CDATA[
-- Matches because the 'f' appears somewhere in 'foo'.
select regexp_like('foo','f');
+-------------------------+
| regexp_like('foo', 'f') |
+-------------------------+
| true |
+-------------------------+
-- Does not match because the comparison is case-sensitive by default.
select regexp_like('foo','F');
+-------------------------+
| regexp_like('foo', 'f') |
+-------------------------+
| false |
+-------------------------+
-- The 3rd argument can change the matching logic, such as 'i' meaning case-insensitive.
select regexp_like('foo','F','i');
+------------------------------+
| regexp_like('foo', 'f', 'i') |
+------------------------------+
| true |
+------------------------------+
-- The familiar regular expression notations work, such as ^ and $ anchors...
select regexp_like('foo','f$');
+--------------------------+
| regexp_like('foo', 'f$') |
+--------------------------+
| false |
+--------------------------+
select regexp_like('foo','o$');
+--------------------------+
| regexp_like('foo', 'o$') |
+--------------------------+
| true |
+--------------------------+
-- ...and repetition operators such as * and +
select regexp_like('foooooobar','fo+b');
+-----------------------------------+
| regexp_like('foooooobar', 'fo+b') |
+-----------------------------------+
| true |
+-----------------------------------+
select regexp_like('foooooobar','fx*y*o*b');
+---------------------------------------+
| regexp_like('foooooobar', 'fx*y*o*b') |
+---------------------------------------+
| true |
+---------------------------------------+
]]>
</codeblock>
</dd>
</dlentry>
<dlentry id="regexp_replace">
<dt>
REGEXP_REPLACE(STRING initial, STRING pattern, STRING replacement)
</dt>
<dd>
<b>Purpose:</b> Returns the initial argument with the regular expression pattern
replaced by the final argument string.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p conref="../shared/impala_common.xml#common/regexp_re2"/>
<p conref="../shared/impala_common.xml#common/regexp_re2_warning"/>
<p conref="../shared/impala_common.xml#common/regexp_escapes"/>
<p conref="../shared/impala_common.xml#common/example_blurb"/>
<p>
These examples show how you can replace parts of a string matching a pattern with
replacement text, which can include backreferences to any <codeph>()</codeph> groups
in the pattern string. The backreference numbers start at 1, and any
<codeph>\</codeph> characters must be escaped as <codeph>\\</codeph>.
</p>
<p>
Replace a character pattern with new text:
</p>
<codeblock>[localhost:21000] &gt; select regexp_replace('aaabbbaaa','b+','xyz');
+------------------------------------------+
| regexp_replace('aaabbbaaa', 'b+', 'xyz') |
+------------------------------------------+
| aaaxyzaaa |
+------------------------------------------+
Returned 1 row(s) in 0.11s</codeblock>
<p>
Replace a character pattern with substitution text that includes the original
matching text:
</p>
<codeblock>[localhost:21000] &gt; select regexp_replace('aaabbbaaa','(b+)','&lt;\\1&gt;');
+----------------------------------------------+
| regexp_replace('aaabbbaaa', '(b+)', '&lt;\\1&gt;') |
+----------------------------------------------+
| aaa&lt;bbb&gt;aaa |
+----------------------------------------------+
Returned 1 row(s) in 0.11s</codeblock>
<p>
Remove all characters that are not digits:
</p>
<codeblock>[localhost:21000] &gt; select regexp_replace('123-456-789','[^[:digit:]]','');
+---------------------------------------------------+
| regexp_replace('123-456-789', '[^[:digit:]]', '') |
+---------------------------------------------------+
| 123456789 |
+---------------------------------------------------+
Returned 1 row(s) in 0.12s</codeblock>
</dd>
</dlentry>
<dlentry id="repeat">
<dt>
REPEAT(STRING str, INT n)
</dt>
<dd>
<b>Purpose:</b> Returns the argument string repeated a specified number of times.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
</dd>
</dlentry>
<dlentry id="replace" rev="2.9.0 IMPALA-4729">
<dt>
REPLACE(STRING initial, STRING target, STRING replacement)
</dt>
<dd>
<b>Purpose:</b> Returns the initial argument with all occurrences of the target string
replaced by the replacement string.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
<p>
Because this function does not use any regular expression patterns, it is typically
faster than <codeph>regexp_replace()</codeph> for simple string substitutions.
</p>
<p>
If any argument is <codeph>NULL</codeph>, the return value is <codeph>NULL</codeph>.
</p>
<p>
Matching is case-sensitive.
</p>
<p>
If the replacement string contains another instance of the target string, the
expansion is only performed once, instead of applying again to the newly constructed
string.
</p>
<p conref="../shared/impala_common.xml#common/added_in_290"/>
<p conref="../shared/impala_common.xml#common/example_blurb"/>
<codeblock>-- Replace one string with another.
select replace('hello world','world','earth');
+------------------------------------------+
| replace('hello world', 'world', 'earth') |
+------------------------------------------+
| hello earth |
+------------------------------------------+
-- All occurrences of the target string are replaced.
select replace('hello world','o','0');
+----------------------------------+
| replace('hello world', 'o', '0') |
+----------------------------------+
| hell0 w0rld |
+----------------------------------+
-- If no match is found, the original string is returned unchanged.
select replace('hello world','xyz','abc');
+--------------------------------------+
| replace('hello world', 'xyz', 'abc') |
+--------------------------------------+
| hello world |
+--------------------------------------+
</codeblock>
</dd>
</dlentry>
<dlentry id="reverse">
<dt>
REVERSE(STRING a)
</dt>
<dd>
<b>Purpose:</b> Returns the argument string with characters in reversed order.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
</dd>
</dlentry>
<dlentry id="right">
<dt>
RIGHT(STRING a, INT num_chars)
</dt>
<dd>
See the <codeph>STRRIGHT()</codeph> function.
</dd>
</dlentry>
<dlentry id="rpad">
<dt>
RPAD(STRING str, INT len, STRING pad)
</dt>
<dd>
<b>Purpose:</b> Returns a string of a specified length, based on the first argument
string. If the specified string is too short, it is padded on the right with a
repeating sequence of the characters from the pad string. If the specified string is
too long, it is truncated on the right.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
</dd>
</dlentry>
<dlentry id="rtrim">
<dt>
RTRIM(STRING a [, STRING chars_to_trim])
</dt>
<dd>
<b>Purpose:</b> Returns the argument string with all occurrences of characters
specified by the second argument removed from the right side. Removes spaces if the
second argument is not specified.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
</dd>
</dlentry>
<dlentry id="space">
<dt>
SPACE(INT n)
</dt>
<dd>
<b>Purpose:</b> Returns a concatenated string of the specified number of spaces.
Shorthand for <codeph>REPEAT(' ',<varname>n</varname>)</codeph>.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
</dd>
</dlentry>
<dlentry rev="2.3.0 IMPALA-2084" id="split_part">
<dt>
SPLIT_PART(STRING source, STRING delimiter, BIGINT n)
</dt>
<dd>
<b>Purpose:</b> Returns the nth field within a delimited string. The fields are
numbered starting from 1. The delimiter can consist of multiple characters, not just a
single character. All matching of the delimiter is done exactly, not using any regular
expression patterns.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p conref="../shared/impala_common.xml#common/regexp_re2"/>
<p conref="../shared/impala_common.xml#common/regexp_re2_warning"/>
<p conref="../shared/impala_common.xml#common/regexp_escapes"/>
<p conref="../shared/impala_common.xml#common/example_blurb"/>
<p>
These examples show how to retrieve the nth field from a delimited string:
</p>
<codeblock><![CDATA[
select split_part('x,y,z',',',1);
+-----------------------------+
| split_part('x,y,z', ',', 1) |
+-----------------------------+
| x |
+-----------------------------+
select split_part('x,y,z',',',2);
+-----------------------------+
| split_part('x,y,z', ',', 2) |
+-----------------------------+
| y |
+-----------------------------+
select split_part('x,y,z',',',3);
+-----------------------------+
| split_part('x,y,z', ',', 3) |
+-----------------------------+
| z |
+-----------------------------+
]]>
</codeblock>
<p>
These examples show what happens for out-of-range field positions. Specifying a
value less than 1 produces an error. Specifying a value greater than the number of
fields returns a zero-length string (which is not the same as
<codeph>NULL</codeph>).
</p>
<codeblock><![CDATA[
select split_part('x,y,z',',',0);
ERROR: Invalid field position: 0
with t1 as (select split_part('x,y,z',',',4) nonexistent_field)
select
nonexistent_field
, concat('[',nonexistent_field,']')
, length(nonexistent_field);
from t1
+-------------------+-------------------------------------+---------------------------+
| nonexistent_field | concat('[', nonexistent_field, ']') | length(nonexistent_field) |
+-------------------+-------------------------------------+---------------------------+
| | [] | 0 |
+-------------------+-------------------------------------+---------------------------+
]]>
</codeblock>
<p>
These examples show how the delimiter can be a multi-character value:
</p>
<codeblock><![CDATA[
select split_part('one***two***three','***',2);
+-------------------------------------------+
| split_part('one***two***three', '***', 2) |
+-------------------------------------------+
| two |
+-------------------------------------------+
select split_part('one\|/two\|/three','\|/',3);
+-------------------------------------------+
| split_part('one\|/two\|/three', '\|/', 3) |
+-------------------------------------------+
| three |
+-------------------------------------------+
]]>
</codeblock>
</dd>
</dlentry>
<dlentry id="strleft">
<dt>
STRLEFT(STRING a, INT num_chars)
</dt>
<dd>
<b>Purpose:</b> Returns the leftmost characters of the string. Shorthand for a call to
<codeph>SUBSTR()</codeph> with 2 arguments.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
</dd>
</dlentry>
<dlentry id="strright">
<dt>
STRRIGHT(STRING a, INT num_chars)
</dt>
<dd>
<b>Purpose:</b> Returns the rightmost characters of the string. Shorthand for a call
to <codeph>SUBSTR()</codeph> with 2 arguments.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
</dd>
</dlentry>
<dlentry id="substr">
<dt>
SUBSTR(STRING a, INT start [, INT len]),
<ph id="substring"
>SUBSTRING(STRING a, INT start [, INT len])</ph>
</dt>
<dd>
<b>Purpose:</b> Returns the portion of the string starting at a specified point,
optionally with a specified maximum length. The characters in the string are indexed
starting at 1.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
</dd>
</dlentry>
<dlentry id="translate">
<dt>
TRANSLATE(STRING input, STRING from, STRING to)
</dt>
<dd>
<b>Purpose:</b> Returns the <codeph>input</codeph> string with each character in the
<codeph>from</codeph> argument replaced with the corresponding character in the
<codeph>to</codeph> argument. The characters are matched in the order they appear in
<codeph>from</codeph> and <codeph>to</codeph>.
<p>
For example: <codeph>translate ('hello world','world','earth')</codeph> returns
<codeph>'hetta earth'</codeph>.
</p>
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p>
<b>Usage notes:</b>
</p>
<p>
If <codeph>from</codeph> contains more characters than <codeph>to</codeph>, the
<codeph>from</codeph> characters that are beyond the length of <codeph>to</codeph>
are removed in the result.
</p>
<p>
For example:
</p>
<p>
<codeph>translate('abcdedg', 'bcd', '1')</codeph> returns <codeph>'a1eg'</codeph>.
</p>
<p>
<codeph>translate('Unit Number#2', '# ', '_')</codeph> returns
<codeph>'UnitNumber_2'</codeph>.
</p>
<p>
If <codeph>from</codeph> is <codeph>NULL</codeph>, the function returns
<codeph>NULL</codeph>.
</p>
<p>
If <codeph>to</codeph> contains more characters than <codeph>from</codeph>, the
extra characters in <codeph>to</codeph> are ignored.
</p>
<p>
If <codeph>from</codeph> contains duplicate characters, the duplicate character is
replaced with the first matching character in <codeph>to</codeph>.
</p>
<p>
For example: <codeph>translate ('hello','ll','67')</codeph> returns
<codeph>'he66o'</codeph>.
</p>
</dd>
</dlentry>
<dlentry id="trim">
<dt>
TRIM(STRING a)
</dt>
<dd>
<b>Purpose:</b> Returns the input string with both leading and trailing spaces
removed. The same as passing the string through both <codeph>LTRIM()</codeph> and
<codeph>RTRIM()</codeph>.
<p>
<b>Usage notes:</b> Often used during data cleansing operations during the ETL
cycle, if input values might still have surrounding spaces. For a more
general-purpose function that can remove other leading and trailing characters
besides spaces, see <codeph>BTRIM()</codeph>.
</p>
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
</dd>
</dlentry>
<dlentry id="upper">
<dt>
UPPER(STRING a), <ph id="ucase">UCASE(STRING a)</ph>
</dt>
<dd>
<b>Purpose:</b> Returns the argument string converted to all-uppercase.
<p>
<b>Return type:</b> <codeph>STRING</codeph>
</p>
<p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
<p
conref="../shared/impala_common.xml#common/case_insensitive_comparisons_tip"
/>
</dd>
</dlentry>
</dl>
</conbody>
</concept>
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