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MySQL实现排名并查询指定用户排名功能

教程 2019-06-22 11:01:18互联网 阅读数:
摘要:说明:@rownum:= @rownum+1中 := 是赋值的作用,这句话的意思是先执行@rownum+1,然后把值赋给@rownum;(SELECT @rownum := 0) r 这句话的意思是设置rownum字段的初始值为0,即编号从1开始...

表结构:

CREATE TABLE test.testsort (

id int(11) NOT NULL AUTO_INCREMENT,

uid int(11) DEFAULT 0 COMMENT '用户id',

score decimal(10, 2) DEFAULT 0.00 COMMENT '分数',

PRIMARY KEY (id)

)

ENGINE = INNODB

AUTO_INCREMENT = 1

CHARACTER SET utf8

COLLATE utf8_general_ci

COMMENT = '测试排序'

ROW_FORMAT = DYNAMIC;

思路:可以先排序,再对结果进行编号;也可以先查询结果,再排序编号。

说明:

@rownum := @rownum + 1 中 := 是赋值的作用,这句话的意思是先执行@rownum + 1,然后把值赋给@rownum;

(SELECT @rownum := 0) r 这句话的意思是设置rownum字段的初始值为0,即编号从1开始。

实现排名:

方法一:

SELECT t.*, @rownum := @rownum + 1 AS rownum

FROM (SELECT @rownum := 0) r, (SELECT * FROM testsort ORDER BY score DESC) AS t;

方法二:

SELECT t.*, @rownum := @rownum + 1 AS rownum

FROM (SELECT @rownum := 0) r, testsort AS t

ORDER BY t.score DESC;

结果:

查看指定用户排名:

方法一:

SELECT b.* FROM

(

SELECT t.*, @rownum := @rownum + 1 AS rownum

FROM (SELECT @rownum := 0) r,

(SELECT * FROM testsort ORDER BY score DESC) AS t

) AS b WHERE b.uid = 222;

方法二:

SELECT b.* from

(

SELECT t.*, @rownum := @rownum + 1 AS rownum

FROM (SELECT @rownum := 0) r, testsort AS t

ORDER BY t.score DESC

) as b where b.uid = 222;

结果:

实现并列排名(相同分数排名相同):

SELECT

obj.uid,

obj.score,

CASE

WHEN @rowtotal = obj.score THEN

@rownum

WHEN @rowtotal := obj.score THEN

@rownum :=@rownum + 1

WHEN @rowtotal = 0 THEN

@rownum :=@rownum + 1

END AS rownum

FROM

(

SELECT

uid,

score

FROM

testsort

ORDER BY

score DESC

) AS obj,

(SELECT @rownum := 0 ,@rowtotal := NULL) r

查询指定用户并列排名:

SELECT total.* FROM

(SELECT

obj.uid,

obj.score,

CASE

WHEN @rowtotal = obj.score THEN

@rownum

WHEN @rowtotal := obj.score THEN

@rownum :=@rownum + 1

WHEN @rowtotal = 0 THEN

@rownum :=@rownum + 1

END AS rownum

FROM

(

SELECT

uid,

score

FROM

testsort

ORDER BY

score DESC

) AS obj,

(SELECT @rownum := 0 ,@rowtotal := NULL) r) AS total WHERE total.uid = 222;

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