The Ultimate Guide to High Availability with MariaDB

WITH

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WITH is a Common table expression (CTE)

WITH allows you to refer to a sub query expression many times in a query. It's like having a temporary table that only exist for the duration of a query.

WITH is supported starting from MariaDB 10.2.1

Syntax

WITH 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 be used with EXPLAIN and SELECT.

Examples

Using WITH on the top level:

WITH t as (select a from t1 where b >= 'c') 
  select * from t2,t where t2.c=t.a;

Using WITH in a sub query:

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);

TODO

We are working on extending WITH for sub queries. MDEV-9864.

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