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[英]How to create update statement using results of sub-query where tables have same column name?
[英]Is there a way to pass an alias column name in a nested sub-query, via WHERE IN statement, to the UPDATE statement?
我碰到了这一点-最近在WHERE中使用ALIAS列,并且我理解了WHERE子句为什么会给我一个错误,但是我似乎无法找出其他任何方式来编写嵌套查询。 SELECT子查询本身可以完全正常运行。
错误如下:
Error Code: 1054. Unknown column 'actual_start_time' in 'IN/ALL/ANY subquery'
表结构:
学生:student_id学生名登陆时间退出时间
测试: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);
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)
);
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