Table is specified twice, both as a target for 'UPDATE' and as a separate source for data

问题:

I am trying to update multiple rows in a column but when I execute query getting error. Somebody guide me where I am wrong. Thanks in advance

  UPDATE TestTaker   SET TestTaker.Email = 'Replaced'   WHERE TestTaker.Id IN (SELECT TestTaker.Id FROM TestTaker   INNER JOIN Questionnaire ON (TestTaker.id = Questionnaire.TestTaker_id)   WHERE Questionnaire.Project_id IN(SELECT Project.Id FROM Project WHERE NAME LIKE 'abcd')); 

回答1:

You are using table 'TestTaker' multiple times in that query, so you have to assign a 'alias' for that table and have to specify this alias for every columns wherever you using. Or try to simplify your query like the below one.

UPDATE TestTaker SET TestTaker.Email = 'Replaced' WHERE TestTaker.Id IN ( SELECT  Questionnaire.TestTaker_id                         FROM    Questionnaire                         WHERE   (TestTaker.id = Questionnaire.TestTaker_id)                             AND Questionnaire.Project_id IN(    SELECT Project.Id                                                                  FROM Project WHERE NAME LIKE 'abcd')                         ); 

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