SQL UPDATE與子查詢引用MySQL中的同一個表

Question

我正在嘗試使用UPDATE更新表中一堆行中的列值。 問題是我需要使用子查詢來派生此列的值，它依賴於同一個表。 這是查詢：

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';

通常，如果老師和學生在兩個不同的表中，mysql不會抱怨。 但由於他們都使用相同的表，mysql反而吐出了這個錯誤：

錯誤1093（HY000）：您無法在FROM子句中為更新指定目標表'student'

有什么辦法可以強制mysql進行更新嗎？ 我100％肯定，因為更新行，所以from子句不會受到影響。

如果沒有，是否有另一種方法可以編寫此更新sql來實現同樣的效果？

謝謝！

編輯：我想我得到了它的工作：

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';

Answer 1

一些參考資料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

Answer 2

具有更清晰的表和列名稱的抽象示例：

UPDATE tableName t1
INNER JOIN tableName t2 ON t2.ref_column = t1.ref_column
SET t1.column_to_update = t2.column_desired_value

正如@Nico所建議的那樣

希望這能有所幫助。

Answer 3

UPDATE user_account 
SET (student_education_facility_id) = ( 
    SELECT teacher.education_facility_id
    FROM user_account teacher
    WHERE teacher.user_account_id = teacher_id
    AND teacher.user_type = 'ROLE_TEACHER'
)
WHERE user_type = 'ROLE_STUDENT'

以上是示例更新查詢...

您可以使用更新SQL語句編寫子查詢，您不需要為該表提供別名。 為別查詢表提供別名。 我試過，它對我來說很好......

Answer 4

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';

Answer 5

我需要這個用於SQL Server。 這里是：

UPDATE user_account 
SET student_education_facility_id = cnt.education_facility_id
from  (
   SELECT user_account_id,education_facility_id
   FROM user_account 
   WHERE user_type = 'ROLE_TEACHER'
) as cnt
WHERE user_account.user_type = 'ROLE_STUDENT' and cnt.user_account_id = user_account.teacher_id

我認為它適用於其他RDBMS（請確認）。 我喜歡語法，因為它是可擴展的。

我需要的格式實際上是：

UPDATE table1 
SET f1 = cnt.computed_column
from  (
   SELECT id,computed_column --can be any complex subquery
   FROM table1
) as cnt
WHERE cnt.id = table1.id

Answer 6

UPDATE user_account student, (
   SELECT teacher.education_facility_id as teacherid
   FROM user_account teacher
   WHERE teacher.user_account_id = student.teacher_id AND teacher.user_type = 'ROLE_TEACHER'
) teach SET student.student_education_facility_id= teach.teacherid WHERE student.user_type = 'ROLE_STUDENT';