在SQL中替换或修剪字符串

Question

I'm pretty good at SQL but I haven't done this in a while.

I have a simple table with a common string:

TableName = ExampleTable1
ColumnName = ExampleColumn1

I have a string like this:

MYSTRING_10_TB_EXAMPLE1
MYSTRING_120_TB_EXAMPLE2

I have this query:

select ExampleColumn1, replace(ExampleColumn1,'MYSTRING_', '') from ExampleTable1

This is returning just the number at the beginning of the string:

"10_TB_EXAMPLE1"

I now need to remove the string after the first dash after the integer. The integer could be either one digit or four or five but I need everything including the first "_" removed or anything that starts with "_TB" to return only the integer.

I know you can use STUFF and replace. I think I need to replace my third parameter in the query of '' with another replace or right maybe?

I have tried many things here and I can't trim the whole string after the first "_" sign to just leave the integer.

Answer 1

Use SUBSTRING_INDEX() function. This query:

SELECT SUBSTRING_INDEX(
  SUBSTRING_INDEX('MYSTRING_120_TB_EXAMPLE2','_',2),
  '_', -1);

will return 120

Answer 2

You can split your string in its parts and continue whatever you want. Try it like this:

DECLARE @tbl TABLE(aString VARCHAR(100));
INSERT INTO @tbl VALUES('MYSTRING_10_TB_EXAMPLE1')
                      ,('MYSTRING_120_TB_EXAMPLE2');

WITH Splitted AS
(
    SELECT CAST('<x>' + REPLACE(aString,'_','</x><x>') + '</x>' AS XML) AS SingleWords
    FROM @tbl
)
SELECT SingleWords.value('x[1]','varchar(max)') AS part1
      ,SingleWords.value('x[2]','int') AS part2
      ,SingleWords.value('x[3]','varchar(max)') AS part3
      ,SingleWords.value('x[4]','varchar(max)') AS part4
FROM Splitted 

/* Result
part1       part2   part3   part4
MYSTRING    10      TB      EXAMPLE1
MYSTRING    120     TB      EXAMPLE2
*/

Just a short explanation: The underscore is replaced by "</x><x>" . With the opening "<x>" at the beginning and the closing "</x>" at the end this is XML. Each node is addressable with its index. That's it...

Answer 3

Use REPLACE to trim away the first part of the string as you've already done.

Use CHARINDEX to find (in the resulting string) the position of the first _

Then use LEFT to keep only the left part of the string up to (but excluding) the first _

SELECT
    ExampleColumn1,
    LEFT( REPLACE(ExampleColumn1,'MYSTRING_', ''),  
       CHARINDEX( REPLACE(ExampleColumn1,'MYSTRING_', ''), '_' ) - 1
    )
FROM 
    ExampleTable1

Would return

MYSTRING_10_TB_EXAMPLE1      10
MYSTRING_120_TB_EXAMPLE2     120

If you're using mySql instead of CHARINDEX use LOCATE :

LOCATE( '_', REPLACE(ExampleColumn1,'MYSTRING_', '') ) - 1