sql 几种循环方式

1:游标方式

ALTER PROCEDURE [dbo].[testpro]  
as

declare @yeardatestr varchar(20) --日期拼接
declare @meterno varchar(20) --仪表编号
declare @collectindataname varchar(30) --数据采集表
declare @collectindataname_back varchar(30) --数据采集备份表


declare @monsdt varchar(20)
declare @monedt varchar(20)

begin


    set @yeardatestr = datename(YY,getdate()) + datename(MM,getdate()) 

    
    set @monsdt=Convert(VarChar(4),DatePart(year,GETDATE()))+'-'+Convert(VarChar(2),DatePart(MONTH,DateAdd(MONTH,-2,GETDATE())))+'-01'
    set @monedt=CONVERT(VARCHAR(10),DateAdd(DAY,-1,DateAdd(MONTH,2,Convert(datetime,@monsdt,121))),20)
    
    declare meters_cur cursor local  fast_forward --定义游标
    for 
    select distinct MeterNo from MeterInfo
    open meters_cur --打开游标
    fetch next from meters_cur into @meterno--从游标中取出数据
    while @@fetch_status =0 --取出数据成功
    begin
    
        dbcc SHRINKFILE(testdb_log,0) --收缩日志 
        fetch next from meters_cur into @meterno--下一条
    end
    close meters_cur--关闭游标
    deallocate meters_cur--释放游标

end

2:goto方式

    nextValue:--循环起点关键字
    select @num=ynum from pp_yunnum where prjsht=@prjsht

    IF(@flg=1)
        set @yunsht='K' + @prjsht + '-' + Convert(varchar(10),@num+1)
    ELSE
        set @yunsht=REPLACE(@prjsht,'_','') + '-' + dbo.Lpad(@num+1,2,'0')

    if exists (select 1 from pp_yun where pp_yun.sht=@yunsht)
    begin
        update pp_yunnum set ynum=ynum+1 where prjsht=@prjsht
        
        goto nextValue;--重新从nextValue出执行
    end