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.............posts id fup title message
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1 asjd;fkja
2 askdjfl;asf
3 asldkfja;sf
.............posts id fup title message
1 1 asd lkasdjf;
2 1 asdklfj alksdjf;asdf
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不过,原文的方法并非效率不高。
如果实在想一次完成,也可以加一些字段来达到这个目的。
从手册的comment里找到一个例子,间接达到了从句用limit的功能,但是
没想出来如何用到楼主的问题上,。楼主的问题更绕人一点
http://dev.mysql.com/doc/mysql/en/row-subqueries.htmlIf you try the following you will find it fails in mysql version 4.1, SELECT
COUNT(*)
FROM
TABLE_1
WHERE
ROW (PK_PART_1, PK_PART_2) IN
(
SELECT
PK_PART_1, PK_PART_2
FROM
TABLE_2
LIMIT
10 -- This is the basis of the whole idea
)
AND
Whatever;The above fails with the warning ... ERROR 1235 (42000): This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME subquery'However, you can get the desired behaviour with a slight rewrite...SELECT
COUNT(*)
FROM
TABLE_1
INNER JOIN
(
SELECT
PK_PART_1, PK_PART_2
FROM
TABLE_2
LIMIT
10 -- HEY HEY!
) AS VIRTUAL_TABLE_2
ON
TABLE_1.PK_PART_1 = TABLE_2.PK_PART_1 AND
TABLE_1.PK_PART_2 = TABLE_2.PK_PART_2
WHERE
Whatever;And it works like a charm!