Question

我坚持使用特定的查询，这很棘手，但我无法解决它。

这里我有一个包含很多行及其列的表格问题（id，subject_id，topic_id，description，pic，cha，pica，chb，picb，chc，picc，chd，picd，answer，attempt，correct，level， checked，BookId，PageNumber）

现在我想更新topic_id为lm的表格问题，要插入的值来自于获取相同表格问题的值，其中topic_id是牛顿

我尝试了3个查询，但它无效：

1＆GT;

UPDATE questions
SET
id = newdata.id,
subject_id = newdata.subject_id,
topic_id = newdata.topic_id,
description = newdata.description,
pic = newdata.pic,
cha = newdata.cha,
pica = newdata.pica,
chb = newdata.chb,
picb = newdata.picb,
chc = newdata.chc,
picc = newdata.picc,
chd = newdata.chd,
picd = newdata.picd,
answer = newdata.answer,
attempt = newdata.attempt,
correct = newdata.correct,
level = newdata.level,
checked = newdata.checked,
BookId = newdata.BookId,
PageNumber = newdata.PageNumber
FROM
(SELECT * FROM questions WHERE topic_id = 'newton') newdata
WHERE
topic_id = 'lm'
AND topic_id = newdata.topic_id;

2＆GT;

UPDATE questions
SET
id = newdata.id,
subject_id = newdata.subject_id,
topic_id = newdata.topic_id,
description = newdata.description,
pic = newdata.pic,
cha = newdata.cha,
pica = newdata.pica,
chb = newdata.chb,
picb = newdata.picb,
chc = newdata.chc,
picc = newdata.picc,
chd = newdata.chd,
picd = newdata.picd,
answer = newdata.answer,
attempt = newdata.attempt,
correct = newdata.correct,
level = newdata.level,
checked = newdata.checked,
BookId = newdata.BookId,
PageNumber = newdata.PageNumber
from questions newdata
WHERE
questions.topic_id = 'lm'
AND newdata.topic_id = 'newton';

3＆GT;

UPDATE questions
SET
id = (SELECT id FROM questions WHERE topid_id = 'newton'),
subject_id = (SELECT subject_id FROM questions WHERE topid_id = 'newton'),
topic_id = (SELECT topic_id FROM questions WHERE topid_id = 'newton'),
description = (SELECT description FROM questions WHERE topid_id = 'newton'),
pic = (SELECT pic FROM questions WHERE topid_id = 'newton'),
cha = (SELECT cha FROM questions WHERE topid_id = 'newton'),
pica = (SELECT pica FROM questions WHERE topid_id = 'newton'),
chb = (SELECT chb FROM questions WHERE topid_id = 'newton'),
picb = (SELECT picb FROM questions WHERE topid_id = 'newton'),
chc = (SELECT chc FROM questions WHERE topid_id = 'newton'),
picc = (SELECT picc FROM questions WHERE topid_id = 'newton'),
chd = (SELECT chd FROM questions WHERE topid_id = 'newton'),
picd = (SELECT picd FROM questions WHERE topid_id = 'newton'),
answer = (SELECT answer FROM questions WHERE topid_id = 'newton'),
attempt = (SELECT attempt FROM questions WHERE topid_id = 'newton'),
correct = (SELECT correct FROM questions WHERE topid_id = 'newton'),
level = (SELECT level FROM questions WHERE topid_id = 'newton'),
checked = (SELECT checked FROM questions WHERE topid_id = 'newton'),
BookId = (SELECT BookId FROM questions WHERE topid_id = 'newton'),
PageNumber = (SELECT PageNumber FROM questions WHERE topid_id = 'newton')
WHERE topic_id = 'lm';

这些都不起作用。

请帮帮我。

如果我犯了任何简单的错误，请道歉。

Answer 1

在MySQL中，除非使用join或过度嵌套的子查询，否则不能在更新中引用同一个表。但是，如果您使用适当的MySQL语法，那么您的查询可能会有效。第一个是：

UPDATE questions q JOIN
       (SELECT * FROM questions WHERE topic_id = 'newton') newdata
       ON q.topic_id = newdata.topic_id
    SET q.id = newdata.id,
        q.subject_id = newdata.subject_id,
        q.topic_id = newdata.topic_id,
        q.description = newdata.description,
        q.pic = newdata.pic,
        q.cha = newdata.cha,
        q.pica = newdata.pica,
        q.chb = newdata.chb,
        q.picb = newdata.picb,
        q.chc = newdata.chc,
        q.picc = newdata.picc,
        q.chd = newdata.chd,
        q.picd = newdata.picd,
        q.answer = newdata.answer,
        q.attempt = newdata.attempt,
        q.correct = newdata.correct,
        q.level = newdata.level,
        q.checked = newdata.checked,
        q.BookId = newdata.BookId,
        q.PageNumber = newdata.PageNumber
WHERE q.topic_id = 'lm';

更新具有条件的行，在同一个表中选择具有另一个条件的行

1 个答案: