SQL基础1

declare @city char(11)                 --声明局部变量select @city = 'Welcome to changsha'   --一次只能给一个变量赋值set @city = 'hehe'                     --一次可以给多个变量赋值  select @city                           --显示变量 select @@version                        --显示版本信息select @@rowcount                       --显示受最近一条语句影响的行数  select ceiling(13.4),   --返回14--不小于13.4的最小整数       floor(13.4),     --返回13--不大于13.4的最大整数         round(13.45678, 2)--结果四舍五入，保留2位小数，输出为4位，其余补0declare @strInfo varchar(40) set @strInfo = 'Welcome to China, I love my Country.'select lower(substring(@strInfo, 1, 6)) as lower,       upper(substring(@strInfo, 9, 5)) as upper--LTRIM删除字符串左边的空格declare @strInfo varchar(33)set @strInfo = '  I love you   'select ltrim(@strInfo)--RTRIM删除字符串右边的空格select rtrim(@strInfo)select left('thank you', 5)--返回字符串左边的5个字符select right('thank you', 5)--返回字符串右边的5个字符--删除第一个字符串从第一个位置开始的5个字符，--然后将第二个字符串插入第一个字符串删除的起始位置select stuff('thank you', 1, 5, 'thank')select reverse('1sads')--反转字符串declare @i smallint, @sum int, @count intset @i = 1set @sum = 0set @count = 0while (@i <= 100)begin    if (@i % 3 = 0)    begin        set @count = @count + 1        set @sum = @sum + @i     end    set @i = @i + 1endprint str(@count) + ',' + str(@sum)use bloggowaitfor delay '00:00:03'  --指定的等待时间格式必须是'hh:mm:ss'select * from userinfo--求1~100的和declare @i smallint, @sum smallintset @i = 1set @sum = 0Label:    if (@i <= 100)    begin       set @sum = @sum + @i       set @i = @i + 1       goto Label    endprint @sum--计算20！declare @sum bigint, @count intset @sum = 1set @count = 1Label:    set @sum = @sum * @count    set @count = @count + 1    if (@count <= 20)        goto Labelprint @sum