mysql sum开窗函数 mysql5.7窗口函数

1、原始数据：SELECT * FROM test_rownumber;

 

 

 

2、ROW_NUMBER功能实现SQL

SELECT * FROM
	(
	SELECT
-- 		当变量@name等于字段值的时候，变量@rn加1，如果不相等赋值为 1
		@rn := CASE WHEN @name = NAME THEN @rn + 1 ELSE 1  END AS rn ,
-- 		把name字段值赋值于变量@name
		@name:=name as name1 ,
		num
	FROM
		( SELECT * FROM test_rownumber ORDER BY name,num DESC ) a,
-- 		初始化一个变量值
		(SELECT @rn = 0,@name=0) b	
	) c