The WITH
keyword signifies a Common Table Expression (CTE). It allows you to refer to a subquery expression many times in a query, as if having a temporary table that only exists for the duration of a query.
There are two kinds of CTEs:
Common Table Expression WITH
was introduced in MariaDB 10.2.1.
Recursive WITH has been supported since MariaDB 10.2.2.
WITH [RECURSIVE] table_reference as (SELECT ...) SELECT ...
You can use table_reference
as any normal table in the external SELECT
part. You can also use WITH
in sub queries. WITH
can also be used with EXPLAIN and SELECT.
Below is an example with the WITH
at the top level:
WITH t AS (SELECT a FROM t1 WHERE b >= 'c') SELECT * FROM t2, t WHERE t2.c = t.a;
The example below uses WITH
in a subquery:
SELECT t1.a, t1.b FROM t1, t2 WHERE t1.a > t2.c AND t2.c IN(WITH t AS (SELECT * FROM t1 WHERE t1.a < 5) SELECT t2.c FROM t2, t WHERE t2.c = t.a);
Below is an example of a Recursive CTE:
WITH RECURSIVE ancestors AS ( SELECT * FROM folks WHERE name="Alex" UNION SELECT f.* FROM folks AS f, ancestors AS a WHERE f.id = a.father OR f.id = a.mother ) SELECT * FROM ancestors;
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https://mariadb.com/kb/en/with/