表結構：
CREATE TABLE test.testsort ( id int(11) NOT NULL AUTO_INCREMENT, uid int(11) DEFAULT 0 COMMENT '用戶id', score decimal(10, 2) DEFAULT 0.00 COMMENT '分數', PRIMARY KEY (id) ) ENGINE = INNODB AUTO_INCREMENT = 1
CHARACTER SET utf8 COLLATE utf8_general_ci COMMENT = '測試排序' ROW_FORMAT = DYNAMIC;
思路：可以先排序，再對結果進行編號；也可以先查詢結果，再排序編號。
說明：
@rownum := @rownum + 1 中 := 是賦值的作用，這句話的意思是先執行@rownum + 1，然后把值賦給@rownum；
(SELECT @rownum := 0) r 這句話的意思是設置rownum字段的初始值為0，即編號從1開始。
實現排名：
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;
結果：
查看指定用戶排名：
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;
結果：
實現從指定用戶uid為111,222,333,444,555 中獲取uid為222的排名
SELECT b.* FROM ( SELECT t.*, @rownum := @rownum + 1 AS rownum FROM (SELECT @rownum := 0) r, (SELECT * FROM testsort WHERE uid IN (111,222,333,444,555) ORDER BY score DESC) AS t ) AS b WHERE b.uid = 222;
結果：
