Using PATINDEX to find varying length patterns in T-SQL

Question

I\'m looking to pull floats out of some varchars, using PATINDEX() to spot them. I know in each varchar string, I\'m only interested in the first float that exists, but they

Answer 1

Yes you need to link to the clr to get regex support. But if PATINDEX does not do what you need then regex was designed exactly for that.

http://msdn.microsoft.com/en-us/magazine/cc163473.aspx

Answer 2

Wildcards.

SELECT PATINDEX('%[0-9]%[0-9].[0-9]%[0-9]%','some text 456.09 other text')
SELECT PATINDEX('%[0-9]%[0-9].[0-9]%[0-9]%','even more text 98273.453 la la la')

Answer 3

Should be checked for robustness (what if you only have an int, for example), but this is just to put you on a track:

if exists (select routine_name from information_schema.routines where routine_name = 'GetFirstFloat')
    drop function GetFirstFloat
go

create function GetFirstFloat (@string varchar(max))
returns float
as
begin
    declare @float varchar(max)
    declare @pos int

    select @pos = patindex('%[0-9]%', @string)
    select @float = ''

    while isnumeric(substring(@string, @pos, 1)) = 1
    begin
        select @float = @float + substring(@string, @pos, 1)
        select @pos = @pos + 1
    end

    return cast(@float as float)
end
go


select dbo.GetFirstFloat('this is a string containing pi 3.14159216 and another non float 3 followed by a new fload 5.41 and that''s it')
select dbo.GetFirstFloat('this is a string with no float')
select dbo.GetFirstFloat('this is another string with an int 3')

Answer 4

PATINDEX is not powerful enough to do that. You should use regular expressions.

SQL Server has Regular expression support since SQL Server 2005.

Answer 5

I blogged about this a while ago. Extracting numbers with SQL server

Declare @Temp Table(Data VarChar(100))

Insert Into @Temp Values('some text 456.09 other text')
Insert Into @Temp Values('even more text 98273.453 la la la')
Insert Into @Temp Values('There are no numbers in this one')

Select Left(
             SubString(Data, PatIndex('%[0-9.-]%', Data), 8000),
             PatIndex('%[^0-9.-]%', SubString(Data, PatIndex('%[0-9.-]%', Data), 8000) + 'X')-1)
From   @Temp

Answer 6

Given that the pattern is going to be varied in length, you're not going to have a rough time getting this to work with PATINDEX. There is another post that I wrote, which I've modified to accomplish what you're trying to do here. Will this work for you?

CREATE TABLE #nums (n INT)
DECLARE @i INT 
SET @i = 1
WHILE @i < 8000 
BEGIN
    INSERT #nums VALUES(@i)
    SET @i = @i + 1
END

CREATE TABLE #tmp (
  id INT IDENTITY(1,1) not null,
  words VARCHAR(MAX) null
)

INSERT INTO #tmp
VALUES('I''m looking for a number, regardless of length, even 23.258 long'),('Maybe even pi which roughly 3.14159265358,'),('or possibly something else that isn''t a number')

UPDATE #tmp SET words = REPLACE(words, ',',' ')

;WITH CTE AS (SELECT ROW_NUMBER() OVER (ORDER BY ID) AS rownum, ID, NULLIF(SUBSTRING(' ' + words + ' ' , n , CHARINDEX(' ' , ' ' + words + ' ' , n) - n) , '') AS word
    FROM #nums, #tmp
    WHERE ID <= LEN(' ' + words + ' ') AND SUBSTRING(' ' + words + ' ' , n - 1, 1) = ' ' 
    AND CHARINDEX(' ' , ' ' + words + ' ' , n) - n > 0),
    ids AS (SELECT ID, MIN(rownum) AS rownum FROM CTE WHERE ISNUMERIC(word) = 1 GROUP BY id)
SELECT CTE.rownum, cte.id, cte.word
FROM CTE, ids WHERE cte.id = ids.id AND cte.rownum = ids.rownum

The explanation and origin of the code is covered in more detail in the origional post