Question

我正在尝试将其转换为使用CASE语句而不是IF语句，但我得到“Set附近的语法不正确”。

它在第一个SET：

WHEN 1 THEN 
   SET @firstOctet = CAST( SUBSTRING( @WorkingNullRouteIP, 1, @lastOctet - 1 ) )


     DECLARE @lastOctet              int,
             @octetCount             int,
             @firstOctet             int = -1,
             @secondOctet            int = -1,
             @thirdOctet             int = -1,
             @fourthOctet            int = -1
     DECLARE @WorkingNullRouteIP     varchar(50)

    SET @WorkingNullRouteIP = @a_NullRouteIP

    WHILE ( CHARINDEX('.',@WorkingNullRouteIP, @lastOctet ) > 0 )
      BEGIN
         SET @lastOctet = CHARINDEX('.',@WorkingNullRouteIP, @lastOctet )
         SET @octetCount = @octetCount + 1

         If @octetCount = 1
            BEGIN
              SET @firstOctet = CAST( SUBSTRING( @WorkingNullRouteIP, 1, @lastOctet - 1 ) )
            END

         If @octetCount = 2
           BEGIN
            SET @secondOctet = CAST( SUBSTRING( @WorkingNullRouteIP, 1, @lastOctet - 1 ) )
           END

         If @octetCount = 3
           BEGIN
            SET @thirdOctet = CAST( SUBSTRING( @WorkingNullRouteIP, 1, @lastOctet - 1 ) )   
           END                                 

         SET @WorkingNullRouteIP = SUBSTRING(@WorkingNullRouteIP, @lastOctet + 1)
         SET @lastOctet = 1
        END     

    -- Converting to this:    

    WHILE ( CHARINDEX('.',@WorkingNullRouteIP, @lastOctet ) > 0 )
     BEGIN
        SET @lastOctet = CHARINDEX('.',@WorkingNullRouteIP, @lastOctet )
        SET @octetCount = @octetCount + 1

        SELECT CASE @octetCount   
             WHEN 1 THEN 
                  SET @firstOctet = CAST( SUBSTRING( @WorkingNullRouteIP, 1, @lastOctet - 1 ) )
             WHEN 2 THEN 
                  SET @secondOctet = CAST( SUBSTRING( @WorkingNullRouteIP, 1, @lastOctet - 1 ) )
             WHEN 3 THEN 
                  SET @thirdOctet = CAST( SUBSTRING( @WorkingNullRouteIP, 1, @lastOctet - 1 ) )                                        
        END

        SET @WorkingNullRouteIP = SUBSTRING(@WorkingNullRouteIP, @lastOctet + 1)
        SET @lastOctet = 1
     END

Answer 1

为什么不使用PARSENAME

所述的here功能

DECLARE @WorkingNullRouteIP     varchar(50) = '192.168.100.1';
DECLARE @firstOctet             int = PARSENAME(@WorkingNullRouteIP,4),
        @secondOctet            int = PARSENAME(@WorkingNullRouteIP,3),
        @thirdOctet             int = PARSENAME(@WorkingNullRouteIP,2),
        @fourthOctet            int = PARSENAME(@WorkingNullRouteIP,1);

select 
     @firstOctet
    ,@secondOctet
    ,@thirdOctet
    ,@fourthOctet;

给予

----------- ----------- ----------- -----------
192         168         100         1

使用CASE语句解析IPv4值

1 个答案: