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sql-servert-sqlpattern-matchingpatindex

Is CHAR(14) not allowed in SQL Server T-SQL patindex range?


What's the problem with CHAR(13) or perhaps CHAR(14) in TSQL patindex? As soon as I include CHAR(14) in a pattern, I get no records found. Searching for an answer, I just found my own question (unanswered) from 2009 (here: http://www.sqlservercentral.com/Forums/Topic795063-338-1.aspx).

Here is another simple test, to show what I mean:

/* PATINDEX TEST */
DECLARE @msg NVARCHAR(255)
SET @msg = 'ABC' + NCHAR(13) + NCHAR(9) + 'DEF'

DECLARE @unwanted NVARCHAR(50)
-- unwanted chars in a "chopped up" string
SET @unwanted = N'%[' + NCHAR(1) + '-' + NCHAR(13) + NCHAR(14) + '-' + NCHAR(31) + ']%'
SELECT patindex(@unwanted, @msg)

-- Result: 4

-- NOW LET THE unwanted string includ the whole range from 1 to 31


   SET @unwanted = '%['+NCHAR(1)+'-'+NCHAR(31)+']%' -- -- As soon as Char(14) is included, we get no match with patindex!
    SELECT patindex(@unwanted, @msg)

-- Result: 0


Solution

  • It is permitted.

    You need to bear in mind that the ranges are based on collation sort order not character codes however so perhaps in your default collation it sorts in a position that you do not expect.

    What is your database's default collation?

    What does the following return?

    ;WITH CTE(N) AS
    (
    SELECT 1 UNION ALL
    SELECT 9 UNION ALL
    SELECT 13 UNION ALL
    SELECT 14 UNION ALL
    SELECT 31 
    )
    SELECT N 
    FROM CTE
    ORDER BY NCHAR(N)
    

    For me it returns

    N
    -----------
    1
    14
    31
    9
    13
    

    So both characters 9 and 13 are outside the range 1-31. Hence

    'ABC' + NCHAR(13) + NCHAR(9) + 'DEF' NOT LIKE N'%['+NCHAR(1)+N'-'+NCHAR(31)+N']%'
    

    Which explains the results in your question. Character 14 doesn't enter into it.

    You can use a binary collate clause to get it to sort more as you were expecting. e.g.

    SELECT patindex(@unwanted COLLATE Latin1_General_100_BIN, @msg)
    

    Returns 4 in the second query too.