Mysql排名功能的实现

drop table if exists t_rank;
CREATE TABLE t_rank
(
pid INT(4) PRIMARY KEY AUTO_INCREMENT,
NAME VARCHAR(20) NOT NULL,
age INT(3),
groupid INT
);

INSERT INTO t_rank(NAME,age,groupid)
VALUES
('Peter', 19, 1),
('Andre',20, 1),
('Vino',20, 3),
('John',25, 3),
('Tom',24, 4),
('Brian',21, 4),
('Andy',22, 3),
('George',23, 4),
('Dew',23, 4),
('Kris',25, 4),
('Samual',25, 4),
('William',26, 2);

-- 相同数值自动排名(没有并列)
SELECT pid, NAME, age, @curRank := @curRank + 1 AS rank
FROM t_rank r,(SELECT @curRank := 0) t
ORDER BY age

-- 相同数值相同排名(无空名次)
SELECT pid, NAME, age,
CASE
WHEN @preRank = age THEN @curRank
WHEN @preRank := age THEN @curRank := @curRank + 1
END AS rank
FROM t_rank r, (SELECT @curRank := 0, @preRank := NULL ) t
ORDER BY age

-- 相同数值相同排名(有空名次)
SELECT pid, NAME, age,
@rownum := @rownum + 1 AS tmp,
@incrnum := CASE
WHEN @rowtotal = age THEN @incrnum
WHEN @rowtotal := age THEN @rownum
END AS rownum
FROM
(
SELECT pid, NAME, age
FROM t_rank
ORDER BY age DESC
) AS a,(SELECT @rownum := 0, @rowtotal := NULL, @incrnum := 0) b

-- 不展示中间过程
select pid,name,age,rownum from (
SELECT pid, NAME, age,
@rownum := @rownum + 1 AS tmp,
@incrnum := CASE
WHEN @rowtotal = age THEN @incrnum
WHEN @rowtotal := age THEN @rownum
END AS rownum
FROM
(
SELECT pid, NAME, age
FROM t_rank
ORDER BY age DESC
) AS a,(SELECT @rownum := 0, @rowtotal := NULL, @incrnum := 0) b) x

SELECT B.data_week,
(SELECT COUNT(1) + 1
FROM (select distinct data_week from bi_user_remain_pay_byweek ) A
WHERE concat(substr(A.data_week,1,4),lpad(substr(A.data_week,6),2,0)) < concat(substr(B.data_week,1,4),lpad(substr(B.data_week,6),2,0))) PM
FROM (select distinct data_week from bi_user_remain_pay_byweek ) B
ORDER BY PM;