sql 经常使用的语句（个人）

--产生随机数 75-85
ROUND(((85 - 75 -1) * RAND() + 75), 0)

--累加更新字段



DECLARE @id numeric

DECLARE @total_electric varchar(20)
DECLARE @total_energy varchar(20)
DECLARE @total_water varchar(20)

DECLARE @total_electricT varchar(20)  
DECLARE @total_energyT varchar(20)
DECLARE @total_waterT varchar(20)

SET @total_electricT=0
SET @total_energyT=0
SET @total_waterT=0

DECLARE My_Cursor CURSOR --定义游标
FOR (SELECT id,total_electric,total_energy,total_water FROM tablename WHERE id>=20320 AND id<=20331) --查出需要的集合放到游标中  
OPEN My_Cursor
FETCH NEXT FROM My_Cursor INTO @id,@total_electric,@total_energy,@total_water

WHILE @@FETCH_STATUS = 0  
    BEGIN  

SET @total_electricT=CONVERT(FLOAT,@total_electricT)+CONVERT(FLOAT,@total_electric)
SET @total_energyT=CONVERT(FLOAT,@total_energyT)+CONVERT(FLOAT,@total_energy)
SET @total_waterT=CONVERT(FLOAT,@total_waterT)+CONVERT(FLOAT,@total_water)

UPDATE tablename SET total_electric=@total_electricT,total_energy=@total_energyT,total_water=@total_waterT WHERE id=@id;

    FETCH NEXT FROM My_Cursor INTO @id,@total_electric,@total_energy,@total_water; --读取下一行数据  
    END  
CLOSE My_Cursor; --关闭游标  
DEALLOCATE My_Cursor; --释放游标  
GO

--float 经常会长度不够变成科学计数法，并且小数位数不可控  用

cast('123.22' as DECIMAL)