— mysql分组排序取前n条记录的最简洁的单条sql。
use test;
drop table if exists test;
CREATE TABLE test ( id INT PRIMARY KEY, cid INT, author VARCHAR(30) ) ENGINE=MYISAM;
INSERT INTO test VALUES (1,1,'test1'), (2,1,'test1'), (3,1,'test2'), (4,1,'test2'), (5,1,'test2'), (6,1,'test3'), (7,1,'test3'), (8,1,'test3'), (9,1,'test3'), (10,2,'test11'), (11,2,'test11'), (12,2,'test22'), (13,2,'test22'), (14,2,'test22'), (15,2,'test33'), (16,2,'test33'), (17,2,'test33'), (18,2,'test33');
INSERT INTO test VALUES (200,200,’200test_nagios’);
select * FROM (SELECT cid,author,COUNT(*) AS number FROM test GROUP BY cid,author) a WHERE N >( SELECT COUNT(*) FROM (SELECT cid,author,COUNT(*) AS number FROM test GROUP BY cid,author) b WHERE a.cid=b.cid AND a.number<b.number><p>结果如下：</p> <pre class="sql">mysql> SELECT * FROM (SELECT cid,author,COUNT(*) AS number FROM test GROUP BY cid,author) a -> WHERE -> 3>( -> SELECT COUNT(*) -> FROM (SELECT cid,author,COUNT(*) AS number FROM test GROUP BY cid,author) b -> WHERE a.cid=b.cid AND a.number<b.number> )ORDER BY cid,number DESC; +------+----------------+--------+ | cid | author | number | +------+----------------+--------+ | 1 | test3 | 4 | | 1 | test2 | 3 | | 1 | test1 | 2 | | 2 | test33 | 4 | | 2 | test22 | 3 | | 2 | test11 | 2 | | 200 | 200test_nagios | 1 | +------+----------------+--------+ 7 rows in set (0.00 sec)</b.number>
N就是取分组之后的最前面几个判断，N=3就是取前3个
— 生成自动数字序列
SET @ROW=0; SELECT a.*,(@ROW:=@ROW +1)Rank FROM test a;
以上就是MySQL分组排序取前N条记录 以及 生成自动数字序列 的SQL的内容，更多相关内容请关注PHP中文网（www.php.cn）！
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