计算min-max两个整数之间的随机整数

Posted 2021-01-05 bgbird

/*------------------------------效率最低
功能：计算min-max两个整数之间的随机整数
作者：
日期：20180831
区别：在查询中嵌入count(*)计算记录总条数，效率最低
*/
--SET STATISTICS IO ON; 
SET STATISTICS TIME ON; 
GO 
DECLARE @min INT= 1;
DECLARE @max INT= 100;
DECLARE @icount INT= 0;
DECLARE @t TABLE
    (
     i INT IDENTITY
           PRIMARY KEY
    ,n INT
    );
INSERT  INTO @t
        (n
        )
        SELECT  FLOOR(RAND(CHECKSUM(NEWID())) * ( @max - @min + 1 )) + @min--计算min-max之间的随机整数
        FROM    master..spt_values AS a
                CROSS JOIN master..spt_values AS b;

                             
SELECT  n
       ,COUNT(n) AS 数量
       ,( SELECT    COUNT(*)
          FROM      @t
        ) AS 总数
       ,COUNT(n) * 100.0 / ( SELECT COUNT(*)
                             FROM   @t
                           ) AS [占比例%]
FROM    @t
GROUP BY n;


/*------------------------------效率居中
功能：计算min-max两个整数之间的随机整数
作者：
日期：20180831
区别：提前计算记录总条数赋值到变量，效率居中
*/
--SET STATISTICS IO ON; 
SET STATISTICS TIME ON; 
GO 
DECLARE @min INT= 1;
DECLARE @max INT= 100;
DECLARE @icount INT= 0;
DECLARE @t TABLE
    (
     i INT IDENTITY
           PRIMARY KEY
    ,n INT
    );
INSERT  INTO @t
        ( n
        )
        SELECT  FLOOR(RAND(CHECKSUM(NEWID())) * ( @max - @min + 1 )) + @min--计算min-max之间的随机整数
        FROM    master..spt_values AS a
                CROSS JOIN master..spt_values AS b;
SELECT  @icount = COUNT(*)
FROM    @t;
                             
SELECT  n
       ,COUNT(n) AS 数量
       ,@icount AS 总数
       ,COUNT(n) * 100.0 / @icount AS [占比例%]
FROM    @t
GROUP BY n;
/*------------------------------效率最高
功能：计算min-max两个整数之间的随机整数
作者：
日期：20180831
区别：根据@@rowcount计算记录总条数，效率最高
*/
--SET STATISTICS IO ON; 
SET STATISTICS TIME ON; 
GO 
DECLARE @min INT= 1;
DECLARE @max INT= 100;
DECLARE @icount INT= 0;
DECLARE @t TABLE
    (
     i INT IDENTITY
           PRIMARY KEY
    ,n INT
    );
INSERT  INTO @t
        (n
        )
        SELECT  FLOOR(RAND(CHECKSUM(NEWID())) * ( @max - @min + 1 )) + @min--计算min-max之间的随机整数
        FROM    master..spt_values AS a
                CROSS JOIN master..spt_values AS b;
SET @icount = @@ROWCOUNT; 
--SET @[email protected]@IDENTITY                     
SELECT  n
       ,COUNT(n) AS 数量
       ,@icount AS 总数
       ,COUNT(n) * 100.0 / @icount AS [占比例%]
FROM    @t
GROUP BY n;