sql - 如何根据条件从另一个表更新表中的列？

Question

我有两张 table

1. 它包含的学生表(Student_id、school_code、name、year、...)
2. 它包含的学校表(school_id、School_code、School_name、year等等......)

我想根据学校代码和年份，使用学校代码表中的 school_id 列更新学生表中的 school_code 列。我有五年的数据。所以 school_id 每年都不同。

我的查询是

UPDATE Master.Student
   SET school_code=( select school_id from Master.school as sc
  JOIN master.student as st
    ON st.school_code=sc.school_code
 WHERE sc.year=x)
 WHERE st.year=x;

但它没有更新。我收到子查询返回多个值的错误。

Answer 1

既然可以直接执行子查询，为什么还要使用子查询？

UPDATE st
  SET st.school_code = sc.school_id 
FROM master.student AS st
  JOIN Master.school AS sc
ON st.school_code = sc.school_code
WHERE sc.year=x
  AND st.year=x;

有关更多信息，请参阅 UPDATE (Transact-SQL)