Monday, 24 September 2018

MySQL UPDATE with SUBQUERY of same table

I want to update a table named "test" with some sub-query where sub-query is the same "test" table. I wrote the below SQL first to update my "test" table:

UPDATE test SET roll=CONCAT(roll,"-",id) WHERE id IN (SELECT id FROM test WHERE id%2=0)

And got below error:

#1093 - Table 'test' is specified twice, both as a target for 'UPDATE' and as a separate source for data.

And in this case we have a nice solution provided by MySQL itself is processing temporary table, query is below:

UPDATE test SET roll=CONCAT(roll,"-",id) WHERE id IN (SELECT t.id FROM (SELECT * FROM test) AS t WHERE t.id%2=0)

And it works. Marked yellow color section actually do the temporary table works.

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