Question

Since it’s not that easy to perform regex in SQL I’ll need some advice in how to solve this problem.

I have a column with the following type of data:

Lorem ipsum dolor sit $%foo##amet%$, consectetur adipiscing elit.
Nullam odio risus, mollis a interdum vitae, rutrum id leo. Pellentesque
dapibus lobortis mattis. Praesent at nisi a orci commodo scelerisque
$%bar##%$ eget id dui. Morbi est arcu, ultricies et consequat ac,
pretium sed mi. Quisque iaculis pretium congue. Etiam ullamcorper sapien
eu mauris tristique at venenatis mauris ultricies. Proin eu vehicula enim.
Vestibulum aliquam, mauris ac tempus vulputate, odio mauris rhoncus purus,
id suscipit velit erat quis magna.

The bold text I need to match, and it needs to be replaced with the text found in the second part.

Meaning:

• $%foo##amet%$ becomes amet
• $%bar##%$ becomes an empty string.

The pattern as a regex would be something like \$%[^#]+?##([^%]*?)%\$

I can’t really use that though since regex is not really supported in tsql…

Any advice?

Answer 1

fixed it with this function:

CREATE FUNCTION [dbo].[ReplaceWithDefault]
(
   @InputString VARCHAR(4000)
)
RETURNS VARCHAR(4000)
AS
BEGIN
    DECLARE @Pattern VARCHAR(100) SET @Pattern = '$[%]_%##%[%]$'
    -- working copy of the string
    DECLARE @Result VARCHAR(4000) SET @Result = @InputString
    -- current match of the pattern
    DECLARE @CurMatch VARCHAR(500) SET @curMatch = ''
    -- string to replace the current match
    DECLARE @Replace VARCHAR(500) SET @Replace = ''
    -- start + end of the current match
    DECLARE @Start INT
    DECLARE @End INT
    -- length of current match
    DECLARE @CurLen INT
    -- Length of the total string -- 8001 if @InputString is NULL
    DECLARE @Len INT SET @Len = COALESCE(LEN(@InputString), 8001)

    WHILE (PATINDEX('%' + @Pattern + '%', @Result) != 0) 
    BEGIN
        SET @Replace = ''

        SET @Start = PATINDEX('%' + @Pattern + '%', @Result)
        SET @CurMatch = SUBSTRING(@Result, @Start, @Len)

        SET @End = PATINDEX('%[%]$%', @CurMatch) + 2
        SET @CurMatch = SUBSTRING(@CurMatch, 0, @End)

        SET @CurLen = LEN(@CurMatch)

        SET @Replace = REPLACE(RIGHT(@CurMatch, @CurLen - (PATINDEX('%##%', @CurMatch)+1)), '%$', '')

        SET @Result = REPLACE(@Result, @CurMatch, @Replace)
    END
    RETURN(@Result)
END