sql 中if、case、while 语法格式

---if语句

declare @ret bit
set @ret=1 --0
if @ret=1 begin
print 'true'
end
else begin
print 'false and null'
end

---多条选择语句
DECLARE @iRet INT, @PKDisp VARCHAR(20)
SET @iRet = 1
-- set @PKDisp='五'
Select @iRet =
CASE
WHEN @PKDisp = '一' THEN 1
WHEN @PKDisp = '二' THEN 2
WHEN @PKDisp = '三' THEN 3
WHEN @PKDisp = '四' THEN 4
WHEN @PKDisp = '五' THEN 5
ELSE 100
END
print @iRet

--while 循环语句

declare @i int
set @i =1
while @i<5 begin
set @i=@i+1
print @i--每次循环的值都输出
end
print @i--输出最后结果值