sql-server - sql server if 语句

Question

我确实遇到过这种情况，我正在尝试使用 if else 进行以下操作。它确实有效，但没有按预期工作。当没有为 preState 选择任何内容时，它将带来 Null I希望它为每个选择显示。你能看看它吗。谢谢大家..我的 if 有问题......“你可以复制并运行它”

       DECLARE     @returnvalue VARCHAR(50)
        ,@state VARCHAR(50)
        ,@i INT
        ,@postState  VARCHAR(50)
        ,@preState  VARCHAR(50)
        ,@Anystring  VARCHAR(255)
        ,@state1 VARCHAR(50)
        ,@state2 VARCHAR(50)

        SET @Anystring='IA all the states Colorado '

      SELECT @state =LTRIM((RTRIM(SUBSTRING(@Anystring, LEN(@Anystring) -      CHARINDEX(' ', REVERSE(@Anystring))+1 , LEN(@Anystring)))))

         SET @state =REPLACE(REPLACE(@Anystring, '.', ' '), '&', ' ')

         set @state1=@state


  SET @i = CHARINDEX(' ',@state1 )

  If (@i > 0 and SUBSTRING(@state1, 1, @i-1) IN ('IA','CO','Iowa','Colorado'))
     begin
     SELECT  @preState = RTRIM(SUBSTRING(@state1, 1, 1)), 
             @state1 = LTRIM(SUBSTRING(@state1, @i+1, 999))
     end

   else IF (@i > 0 and SUBSTRING(@state, 1, @i-1) IN ('DC','SEA','NY'))
     begin
     SELECT  @preState = RTRIM(SUBSTRING(@state1, 1, 2)), 
             @state1 = LTRIM(SUBSTRING(@state1, @i+1, 999))

     end        


   SET @i = LEN(@state1) - CHARINDEX(' ', REVERSE(rtrim(@state1)))
  IF (@i > 0 and @i < LEN(@Anystring) and SUBSTRING(@state1, @i+2, 999) IN     ('IA','CO','Iowa','Colorado')) 
      begin
     SELECT @postState = SUBSTRING(@state1, @i+2, 1),
             @state1 = RTRIM(SUBSTRING(@state1, 1, @i))
      end       

else IF (@i > 0 and @i < len(@state)  and SUBSTRING(@state1, @i+2, 999) IN ('DC','SEA','NY')) 
    begin
     SELECT @postState = SUBSTRING(@state1, @i+2, 2),
             @state1 = RTRIM(SUBSTRING(@state1, 1, @i))
    end         

else IF (@i > 0 and SUBSTRING(@state1, 1, @i-1) IN ('','  ','   '))  
        begin

        SELECT @postState = '',
             @state1 = LTRIM(SUBSTRING(@state1, 1, 999))          
        end           
      SET  @state1=@preState+' ' + @state1+' '+@postState 

      set @state2=@state1


      select @state2

Answer 1

如果你的意思是你从中得到 NULL

SET  @state1=@preState+' ' + @state1+' '+@postState 

然后你会想要 ISNULL 它来处理缺少前缀

SET  @state1= isnull(@preState+' ','') + @state1+' '+@postState 

@poststate 也是如此