I'm trying to update a column's value in a bunch of rows in a table using UPDATE. The problem is that I need to use a sub-query to derive the value for this column, and it depends on the same table. Here's the query:
UPDATE user_account student
SET student.student_education_facility_id = (
SELECT teacher.education_facility_id
FROM user_account teacher
WHERE teacher.user_account_id = student.teacher_id AND teacher.user_type = 'ROLE_TEACHER'
)
WHERE student.user_type = 'ROLE_STUDENT';
Ordinarily if teacher and student were in 2 different tables, mysql wouldn't complain. But since they are both using the same table, mysql spews out this error instead:
ERROR 1093 (HY000): You can't specify target table 'student' for update in FROM clause
Is there any way I can force mysql to do the update? I am 100% positive the from clause will not be affected as the rows are updated.
If not, is there another way I can write this update sql to achieve the same affect?
Thanks!
EDIT: I think I got it to work:
UPDATE user_account student
LEFT JOIN user_account teacher ON teacher.user_account_id = student.teacher_id
SET student.student_education_facility_id = teacher.education_facility_id
WHERE student.user_type = 'ROLE_STUDENT';
Some reference for you http://dev.mysql.com/doc/refman/5.0/en/update.html
UPDATE user_account student
INNER JOIN user_account teacher ON
teacher.user_account_id = student.teacher_id
AND teacher.user_type = 'ROLE_TEACHER'
SET student.student_education_facility_id = teacher.education_facility_id