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  1. MariaDB Server
  2. MDEV-25002

ON expressions cannot contain outer references

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      Description

      Outside references in LEFT JOIN's ON expression produce "unknown column" error.

      Create the test dataset (As far as I'm aware, there's nothing special about this choice of tables/columns):

      create table t10 (
        pk int primary key,
        a int
      );
      insert into t10 values (1,1);
       
      create table t11 (
        pk int primary key,
        b int
      );
      create table t12 (a int);
      insert into t12 values (1),(2);
      

      Run the query Q1:

      select
        a,
        (select count(*)
         from 
           t10 left join t11 on t11.pk=t12.a
         where 
           t10.pk=1
         ) as SUBQ
      from t12;
      

      ERROR 1054 (42S22): Unknown column 't12.a' in 'on clause'
      

      Wrapping the outside reference in a subquery helps: Q2:

      select
        a,
        (select count(*)
         from 
           t10 left join t11 on t11.pk=(select t12.a from dual)
         where 
           t10.pk=1
         ) as SUBQ
      from t12;
      

      +------+------+
      | a    | SUBQ |
      +------+------+
      |    1 |    1 |
      |    2 |    1 |
      +------+------+
      

      I've tried Q1 on MySQL 8.0.22 or PostgreSQL and it worked in both.

      Is it a bug MariaDB produces this error?

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            Assignee:
            igor Igor Babaev
            Reporter:
            psergei Sergei Petrunia
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              Created:
              Updated:
              Resolved: