impala/docs/topics/impala_boolean.xml

<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="boolean">

  <title>BOOLEAN Data Type</title>
  <titlealts audience="PDF"><navtitle>BOOLEAN</navtitle></titlealts>
  <prolog>
    <metadata>
      <data name="Category" value="Impala"/>
      <data name="Category" value="Impala Data Types"/>
      <data name="Category" value="SQL"/>
      <data name="Category" value="Data Analysts"/>
      <data name="Category" value="Developers"/>
      <data name="Category" value="Schemas"/>
    </metadata>
  </prolog>

  <conbody>

    <p>
      A data type used in <codeph>CREATE TABLE</codeph> and <codeph>ALTER TABLE</codeph> statements, representing a
      single true/false choice.
    </p>

    <p conref="../shared/impala_common.xml#common/syntax_blurb"/>

    <p>
      In the column definition of a <codeph>CREATE TABLE</codeph> statement:
    </p>

<codeblock><varname>column_name</varname> BOOLEAN</codeblock>

    <p>
      <b>Range:</b> <codeph>TRUE</codeph> or <codeph>FALSE</codeph>. Do not use quotation marks around the
      <codeph>TRUE</codeph> and <codeph>FALSE</codeph> literal values. You can write the literal values in
      uppercase, lowercase, or mixed case. The values queried from a table are always returned in lowercase,
      <codeph>true</codeph> or <codeph>false</codeph>.
    </p>

    <p>
      <b>Conversions:</b> Impala does not automatically convert any other type to <codeph>BOOLEAN</codeph>. All
      conversions must use an explicit call to the <codeph>CAST()</codeph> function.
    </p>

    <p>
      You can use <codeph>CAST()</codeph> to convert
<!--
      <codeph>TINYINT</codeph>, <codeph>SMALLINT</codeph>,
      <codeph>INT</codeph>, <codeph>BIGINT</codeph>, <codeph>FLOAT</codeph>, or <codeph>DOUBLE</codeph>
-->
      any integer or floating-point type to
      <codeph>BOOLEAN</codeph>: a value of 0 represents <codeph>false</codeph>, and any non-zero value is converted
      to <codeph>true</codeph>.
    </p>

<codeblock>SELECT CAST(42 AS BOOLEAN) AS nonzero_int, CAST(99.44 AS BOOLEAN) AS nonzero_decimal,
  CAST(000 AS BOOLEAN) AS zero_int, CAST(0.0 AS BOOLEAN) AS zero_decimal;
+-------------+-----------------+----------+--------------+
| nonzero_int | nonzero_decimal | zero_int | zero_decimal |
+-------------+-----------------+----------+--------------+
| true        | true            | false    | false        |
+-------------+-----------------+----------+--------------+
</codeblock>

    <p>
      When you cast the opposite way, from <codeph>BOOLEAN</codeph> to a numeric type,
      the result becomes either 1 or 0:
    </p>

<codeblock>SELECT CAST(true AS INT) AS true_int, CAST(true AS DOUBLE) AS true_double,
  CAST(false AS INT) AS false_int, CAST(false AS DOUBLE) AS false_double;
+----------+-------------+-----------+--------------+
| true_int | true_double | false_int | false_double |
+----------+-------------+-----------+--------------+
| 1        | 1           | 0         | 0            |
+----------+-------------+-----------+--------------+
</codeblock>

    <p rev="1.4.0">
<!-- BOOLEAN-to-DECIMAL casting requested in IMPALA-991. As of Sept. 2014, designated "won't fix". -->
      You can cast <codeph>DECIMAL</codeph> values to <codeph>BOOLEAN</codeph>, with the same treatment of zero and
      non-zero values as the other numeric types. You cannot cast a <codeph>BOOLEAN</codeph> to a
      <codeph>DECIMAL</codeph>.
    </p>

    <p>
      You cannot cast a <codeph>STRING</codeph> value to <codeph>BOOLEAN</codeph>, although you can cast a
      <codeph>BOOLEAN</codeph> value to <codeph>STRING</codeph>, returning <codeph>'1'</codeph> for
      <codeph>true</codeph> values and <codeph>'0'</codeph> for <codeph>false</codeph> values.
    </p>

    <p>
      Although you can cast a <codeph>TIMESTAMP</codeph> to a <codeph>BOOLEAN</codeph> or a
      <codeph>BOOLEAN</codeph> to a <codeph>TIMESTAMP</codeph>, the results are unlikely to be useful. Any non-zero
      <codeph>TIMESTAMP</codeph> (that is, any value other than <codeph>1970-01-01 00:00:00</codeph>) becomes
      <codeph>TRUE</codeph> when converted to <codeph>BOOLEAN</codeph>, while <codeph>1970-01-01 00:00:00</codeph>
      becomes <codeph>FALSE</codeph>. A value of <codeph>FALSE</codeph> becomes <codeph>1970-01-01
      00:00:00</codeph> when converted to <codeph>BOOLEAN</codeph>, and <codeph>TRUE</codeph> becomes one second
      past this epoch date, that is, <codeph>1970-01-01 00:00:01</codeph>.
    </p>

    <p conref="../shared/impala_common.xml#common/null_null_arguments"/>

    <p conref="../shared/impala_common.xml#common/partitioning_blurb"/>

    <p>
      Do not use a <codeph>BOOLEAN</codeph> column as a partition key. Although you can create such a table,
      subsequent operations produce errors:
    </p>

<codeblock>[localhost:21000] &gt; create table truth_table (assertion string) partitioned by (truth boolean);
[localhost:21000] &gt; insert into truth_table values ('Pigs can fly',false);
ERROR: AnalysisException: INSERT into table with BOOLEAN partition column (truth) is not supported: partitioning.truth_table
</codeblock>

    <p conref="../shared/impala_common.xml#common/example_blurb"/>

<codeblock>SELECT 1 &lt; 2;
SELECT 2 = 5;
SELECT 100 &lt; NULL, 100 &gt; NULL;
CREATE TABLE assertions (claim STRING, really BOOLEAN);
INSERT INTO assertions VALUES
  ("1 is less than 2", 1 &lt; 2),
  ("2 is the same as 5", 2 = 5),
  ("Grass is green", true),
  ("The moon is made of green cheese", false);
SELECT claim FROM assertions WHERE really = TRUE;
</codeblock>

    <p conref="../shared/impala_common.xml#common/hbase_ok"/>

    <p conref="../shared/impala_common.xml#common/parquet_ok"/>

    <p conref="../shared/impala_common.xml#common/text_bulky"/>

<!-- <p conref="../shared/impala_common.xml#common/compatibility_blurb"/> -->

<!-- <p conref="../shared/impala_common.xml#common/internals_blurb"/> -->

<!-- <p conref="../shared/impala_common.xml#common/added_in_20"/> -->

    <p conref="../shared/impala_common.xml#common/column_stats_constant"/>

<!-- <p conref="../shared/impala_common.xml#common/restrictions_blurb"/> -->

<!-- <p conref="../shared/impala_common.xml#common/related_info"/> -->

    <p>
      <b>Related information:</b> <xref href="impala_literals.xml#boolean_literals"/>,
      <xref href="impala_operators.xml#operators"/>,
      <xref href="impala_conditional_functions.xml#conditional_functions"/>
    </p>
  </conbody>
</concept>