从SQL Server中的字符串末尾提取子字符串

Question

I have following string :

DECLARE @build_names VARCHAR(5000) = NULL; 

SET @build_names = 'BB10-1_X-4759-566549'; 

i want to extract it from the last, - is the delimiter. The string will be extracted into 3 sub-strings ie 566549 , 4759 , BB10-1_X .

Please help me, I am a beginner.

Answer 1

You can use charindex() and reverse() to get your desired results:

declare @temp varchar(40)
set @temp = 'BB10-1_X-4759-566549'

select @temp, REVERSE(@temp)
select REVERSE(substring(REVERSE(@temp),0,CHARINDEX('-',REVERSE(@temp),0)))

Give this a shot. It answers your first question of extracting from after the last - of the string.

The next part of your question seems to indicate that you want to split the entire thing up based on the - . Using stored procedures or functions will fail because you want BB10-1_X to be a single string. So if these strings are always in this format of having exactly three - 's but you only want 3 substrings, you can hard code it like this.

declare @temp varchar(40), @reverse varchar(40), @sub1 varchar(20), @sub2 varchar(20), @sub3 varchar(20)

SET @temp = 'BB10-1_X-4759-566549'
SET @reverse = REVERSE(@temp)

SET @sub3 = REVERSE(substring(@reverse,0,CHARINDEX('-',@reverse,0)))

SELECT @temp = substring(@temp,0,charindex(REVERSE(substring(@reverse,0,CHARINDEX('-',@reverse,0))),@temp,0)-1)
SELECT @reverse = REVERSE(@temp)

SET @sub2 = REVERSE(SUBSTRING(@reverse,0,CHARINDEX('-', @reverse, 0)))
SET @sub1 = REVERSE(SUBSTRING(@reverse,CHARINDEX('-',@reverse,0)+1,LEN(@temp)-CHARINDEX('-',@reverse,0)))

select @sub1, @sub2, @sub3

Answer 2

There has been a lot written on efficient splitting functions for TSQL. I suspect that diving into that is probably overkill for this question as it is very specific.

Here's something that demostrate some basic TSQL string manipulation.

NOTE: I use a common table expression (CTE) for clarity, but those manipulations could be done in line.

DECLARE @build_names VARCHAR(5000) = NULL

SET @build_names = 'BB10-1_X-4759-566549'

;WITH cte AS (
 SELECT CHARINDEX('-',REVERSE(@build_names),1) RevPosLastSep
       ,CHARINDEX('-',@build_names,CHARINDEX('-',@build_names,1)+1) PosFirstSep
)
SELECT RIGHT(@build_names,RevPosLastSep-1)
      ,SUBSTRING(@build_names,PosFirstSep+1,LEN(@build_names) - RevPosLastSep - PosFirstSep)
      ,LEFT(@build_names,PosFirstSep-1)
  FROM cte

Answer 3

You might want to create split function

CREATE FUNCTION [dbo].[fnSplitString] 
( 
@string NVARCHAR(MAX), 
@delimiter CHAR(1) 
) 
RETURNS @output TABLE(splitdata NVARCHAR(MAX) 
) 
BEGIN 
DECLARE @start INT, @end INT 
SELECT @start = 1, @end = CHARINDEX(@delimiter, @string) 
WHILE @start < LEN(@string) + 1 BEGIN 
    IF @end = 0  
        SET @end = LEN(@string) + 1

    INSERT INTO @output (splitdata)  
    VALUES(SUBSTRING(@string, @start, @end - @start)) 
    SET @start = @end + 1 
    SET @end = CHARINDEX(@delimiter, @string, @start)

END 
RETURN 
END

Exceute this T-sql statements to create function and use as

select 4,3,1+'-'+2 from dbo.fnSplitString('BB10-1_X-4759-566549','-')

source: http://www.sqlservercentral.com/blogs/querying-microsoft-sql-server/2013/09/19/how-to-split-a-string-by-delimited-char-in-sql-server/