The OFFSET clause in a SELECT query causes the result set to start some
number of rows after the logical first item. The result set is numbered starting from zero, so OFFSET
0 produces the same result as leaving out the OFFSET clause. Always use this clause
in combination with ORDER BY (so that it is clear which item should be first, second, and so
on) and LIMIT (so that the result set covers a bounded range, such as items 0-9, 100-199,
and so on).
The following example shows how you could run a paging
query originally written for a traditional
database application. Because typical Impala queries process megabytes or gigabytes of data and read large
data files from disk each time, it is inefficient to run a separate query to retrieve each small group of
items. Use this technique only for compatibility while porting older applications, then rewrite the
application code to use a single query with a large result set, and display pages of results from the cached
result set.
[localhost:21000] > create table numbers (x int);
[localhost:21000] > insert into numbers select x from very_long_sequence;
Inserted 1000000 rows in 1.34s
[localhost:21000] > select x from numbers order by x limit 5 offset 0;
+----+
| x |
+----+
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
+----+
[localhost:21000] > select x from numbers order by x limit 5 offset 5;
+----+
| x |
+----+
| 6 |
| 7 |
| 8 |
| 9 |
| 10 |
+----+