有没有办法通过 WHERE IN 语句将嵌套子查询中的别名列名传递给 UPDATE 语句？

Question

我遇到了这个 - Using ALIAS column in WHERE 最近，我明白了为什么 WHERE 子句给我一个错误，但我似乎无法想出任何其他方式来编写我的嵌套查询。 SELECT 子查询本身运行完全正常。

错误如下：

Error Code: 1054. Unknown column 'actual_start_time' in 'IN/ALL/ANY subquery'

Table Structure:

Students:    student_id    student_name    login_time    logout_time

Tests:    test_id    test_start_time    test_end_time

TestStats:    test_id    student_id    test_duration

UPDATE test_stats
SET test_duration = datediff(hour, actual_start_time - actual_end_time)
WHERE (actual_start_time, actual_end_time)
IN (
SELECT
CASE
WHEN (s.login_time > t.test_start_time) THEN s.login_time
ELSE t.test_start_time
END AS actual_start_time,
CASE
WHEN (s.logout_time < t.test_end_time) THEN s.logout_time
ELSE t.test_end_time
END AS actual_end_time
FROM tests AS t, students AS s, test_stats AS ts
WHERE t.test_id = ts.test_id and s.student_id = ts.student_id);

Answer 1

这似乎是您想要的：

UPDATE test_stats ts JOIN
       tests t
       ON t.test_id = ts.test_id  JOIN
       students s
       ON s.student_id = ts.student_id
SET test_duration = timestampdiff(hour,
                                  GREATEST(s.login_time, t.test_start_time),
                                  LEAST(s.logout_time, t.test_end_time)
                                 );

有没有办法通过 WHERE IN 语句将嵌套子查询中的别名列名传递给 UPDATE 语句？

Is there a way to pass an alias column name in a nested sub-query, via WHERE IN statement, to the UPDATE statement?

mysql

sql

case

where

sql-update