MySQL Equivalent Query or JOIN query

MySQL

The query below works pefectly in SQL Server

update userrole 
set userid = 6 where userid = 5
and id not in 
(
  select b.id from userrole a inner join userrole b
  on a.roleid = b.roleid and a.region = b.region
  where a.userid = 6 and b.userid = 5
)

When I use the same query in MYSQL, I get the exception 1093 which says Error Code: 1093. You can't specify target table 'userrole' for update in FROM clause.

How to change the query to MySQL equivalent?
How to use JOIN query instead of sub-query in the above query

Thanks in advance.

Best Answer

If you don 't try to understand the meaning of the request and simply adapt it to MySQL then:

UPDATE userrole ur
LEFT JOIN ( SELECT b.id 
            FROM userrole a 
            INNER JOIN userrole b ON a.roleid = b.roleid 
                                 AND a.region = b.region
            WHERE a.userid = 6 
              AND b.userid = 5 ) sq ON ur.id = sq.id
SET ur.userid = 6 
WHERE ur.userid = 5
WHERE sq.id IS NULL

If you try to understand the task then it looks like (it seems) "alter userid from 5 to 6 if the record with the same (roleid,region) and userid=6 not exists yet". If so the task may be solved by:

UPDATE userrole t1
LEFT JOIN userrole t2 ON (t1.roleid, t1.region) = (t2.roleid, t2.region)
                     AND t2.userid = 6
SET t1.userid = 6
WHERE t1.useris = 5
  AND t2.userid IS NULL

Related Solutions

Mysql – Convert Oracle query to MySQL

Try using an UPDATE JOIN of the table against itself

UPDATE
    animal_table A
INNER JOIN
(
    SELECT
        category_id,summary_id,
        animal_nbr,animal_amount,'00' info3
    FROM animal_table
    WHERE animal_type = 'special'
) B USING (category_id,summary_id)
SET
    A.animal_info1 = B.animal_nbr,
    A.animal_info2 = B.animal_amount,
    A.animal_info3 = B.info3
WHERE
    A.animal_type = 'cats' AND
    A.category_id = 'foo';

Make sure that animal_table has a compound index on category_id and summary_id. If you do not have such an index, please run this:

ALTER TABLE animal_table ADD INDEX (category_id,summary_id);

UPDATE 2011-09-27 13:10 EDT

I just noticed that categrory_id 'foo' limits the dataset. Here is an updated refactoring of my answer ( I moved category_id = foo into the subquery )

UPDATE
    animal_table A
INNER JOIN
(
    SELECT
        category_id,summary_id,
        animal_nbr,animal_amount,'00' info3
    FROM animal_table
    WHERE animal_type = 'special'
    AND category_id = 'foo'
) B USING (category_id,summary_id)
SET
    A.animal_info1 = B.animal_nbr,
    A.animal_info2 = B.animal_amount,
    A.animal_info3 = B.info3
WHERE
    A.animal_type = 'cats';

I also recommend adding this additional index to accommodate the subquery

ALTER TABLE animal_table ADD INDEX (animal_type,category_id);

Mysql – Problem with nested UPDATE queries

Try

UPDATE Tab1 JOIN Tab2 ON Tab1.b = Tab2.b
SET Tab1.a = '3'
WHERE Tab1.c = '4'
;

Check the documentation for further information (look for 'multiple-table syntax'). An important point is:

If you use a multiple-table UPDATE statement involving InnoDB tables for which there are foreign key constraints, the MySQL optimizer might process tables in an order that differs from that of their parent/child relationship. In this case, the statement fails and rolls back. Instead, update a single table and rely on the ON UPDATE capabilities that InnoDB provides to cause the other tables to be modified accordingly. See Section 14.3.5.4, “FOREIGN KEY Constraints”.

You may check a similar example on SQLFiddle.

Best Answer

Related Solutions

Mysql – Convert Oracle query to MySQL

Mysql – Problem with nested UPDATE queries

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