1、原始數據：SELECT * FROM test_rownumber;
2、ROW_NUMBER功能實現SQL
SELECT * FROM
(
SELECT
-- 當變量@name等於字段值的時候，變量@rn加1，如果不相等賦值為 1
@rn := CASE WHEN @name = NAME THEN @rn + 1 ELSE 1 END AS rn ,
-- 把name字段值賦值於變量@name
@name:=name as name1 ,
num
FROM
( SELECT * FROM test_rownumber ORDER BY name,num DESC ) a,
-- 初始化一個變量值
(SELECT @rn = 0,@name=0) b
) c
