使用引用 MySQL 中同一表的子查询的 SQL UPDATE

Question

我正在尝试使用 UPDATE 更新表中一堆行中的列值。问题是我需要使用子查询来导出该列的值，并且它依赖于同一个表。查询如下：

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，如果教师和学生位于两个不同的表中，mysql 不会抱怨。但由于它们都使用同一个表，mysql反而会输出这个错误：

ERROR 1093 (HY000): You can't指定目标表'student'在FROM子句中进行更新

有什么办法吗？可以强制mysql进行更新吗？我 100% 肯定 from 子句不会因行更新而受到影响。

如果没有，是否有另一种方法可以编写此更新sql来达到相同的效果？

谢谢！

编辑：我想我让它工作了：

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

给你一些参考 http://dev.mysql.com/doc/refman/5.0/en/更新.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称的抽象示例：

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 希望

这对某人有帮助。

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'

上面是示例更新查询...

您可以使用更新 SQL 语句编写子查询，不需要为该表提供别名。为子查询表提供别名。我尝试过，它对我来说效果很好......

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

我需要这个用于 SQL Server。就是这样：

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

我认为它可以与其他 RDBMS 一起使用（请确认）。我喜欢这种语法，因为它是可扩展的。

我需要的格式实际上是这样的：

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

我需要在子查询中求和，但没有一个解决方案有效。
因此，我在主表上创建了一个视图，并且可以从中访问同一个表。

创建 user_account_VW 作为 select * from user_account

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

Answer 7

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';