mysql数据库语句，如果我要更新某个数据类型的总条数，同时还得查询

Question

我是这样写的：
一、
UPDATE computertype SET typecount= SELECT COUNT(*) AS COUNT FROM computertype WHERE TYPE = '计算机网络基础学测题库'

意思是，我想更新 typecount的数据，但同时我得查询出这个TYPE某个数据的总条数给 typecount

这个是要怎么写?

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二、
另外，我还想把TYPE也自动写入，即：

UPDATE computertype SET typecount= SELECT COUNT(*) AS COUNT FROM computertype WHERE TYPE = SELECT DISTINCT TYPE FROM computertype

这个又要怎么写？

求大佬指点一二，谢谢！

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第一个问题解决了，谢谢
第二个问题意思是：

SELECT DISTINCT TYPE FROM computertype 这个语句，得到的是：5G初级题库（新）、计算机网络基础学测题库、02141计算机网络技术。 这个语句是得到不重复的type数据。

我想进行结合。

我是这样写的，就是想能不能类似一种遍历的方式，把这个不同类型的typecount数据给更新了

UPDATE computertype SET typecount = (SELECT FROM (SELECT COUNT() AS COUNT FROM computertype WHERE TYPE = SELECT DISTINCT TYPE FROM computertype ) AS COUNT) WHERE TYPE = SELECT DISTINCT TYPE FROM computertype

但是报错了

Answer 1

第一个：

update computertype set typecount = (select * from (SELECT COUNT(*) AS COUNT FROM computertype WHERE TYPE = '计算机网络基础学测题库') as count)

第二个

UPDATE computertype
SET typecount = (SELECT *
                 FROM (SELECT COUNT() AS COUNT
                       FROM computertype
                       WHERE TYPE =
                       (select * from (SELECT DISTINCT TYPE
                                       FROM computertype) as a)) AS COUNT)
WHERE TYPE = (select * from (SELECT DISTINCT TYPE
                             FROM computertype) as b)

在 mysql 里面，右值如果是 (select * from table) 语句，必须符合 (select * from (select * from table) as x) 的形式。

Answer 2

没读懂需求，猜你是需要这样吧

UPDATE `computertype` a,
(
    SELECT `TYPE`, COUNT(1) AS `cnt`
    FROM `computertype`
    GROUP BY `TYPE`
) b
SET a.`typecount` = b.`cnt`
WHERE a.`TYPE` = b.`TYPE`;

Answer 3

#直接连表更新操作即可
UPDATE computertype AS ct,
 (
    SELECT
        `type`,
        count(*) AS `count`
    FROM
        computertype
    GROUP BY
        `type`
) AS tc
SET ct.typecount = tc.`count`
WHERE
    ct.`type` = tc.`type`;