Extracting specific column values embedded within composite Strings of codes - sql

Question

I am trying to create a piece of code in sql server 2008 that will grab specific values from each distinct string within my dbo table. The ultimate goal is to make a drop down box within Visual Studio so that one can choose all lines from the database that contain a specific product code (see definition of product code below). Example strings:
in_0314_95pf_500_w_0315
in_0314_500_95pf_0315_w
The part of these strings I am wishing to identify is the 3 digit numeric code (in this case let us call it product code) that appears once within each string. There are roughly 300 different product codes.
The problem is that these product code values do not appear in the same position within each unique string. Hence, I am having a hard time determining the product code because I can't use substring, charindex, like, etc.
Any ideas? Any help is MUCH appreciated.

Answer 1

This can be done with PATINDEX:
DECLARE #s NVARCHAR(100) = 'in_0314_95pf_500_w_0315'
SELECT SUBSTRING(#s, PATINDEX('%[_][0-9][0-9][0-9][_]%', #s) + 1, 3)
Output:
500
If there are no underscores then:
SELECT SUBSTRING(#s, PATINDEX('%[^0-9][0-9][0-9][0-9][^0-9]%', #s) + 1, 3)
This means 3 digits between any symbols that are not digits.
EDIT:
Apply to table like:
SELECT SUBSTRING(ColumnName, PATINDEX('%[^0-9][0-9][0-9][0-9][^0-9]%', ColumnName) + 1, 3)
FROM TableName

Answer 2

One approach is to use a String splitting table function like this one which breaks the string up into its components. You can then filter the components based on your criteria:
SELECT Name
FROM dbo.splitstring('in_0314_95pf_500_w_0315', '_')
WHERE ISNUMERIC(Name) = 1 AND LEN(Name) = 3;
I've amended the function slightly to accept the delimiter as a parameter.
CREATE FUNCTION dbo.splitstring ( #stringToSplit VARCHAR(MAX), #delimiter VARCHAR(50))
RETURNS
#returnList TABLE ([Name] [nvarchar] (500))
AS
BEGIN
DECLARE #name NVARCHAR(255)
DECLARE #pos INT
WHILE CHARINDEX(#delimiter, #stringToSplit) > 0
BEGIN
SELECT #pos = CHARINDEX(#delimiter, #stringToSplit)
SELECT #name = SUBSTRING(#stringToSplit, len(#delimiter), #pos-len(#delimiter))
INSERT INTO #returnList
SELECT #name
SELECT #stringToSplit = SUBSTRING(#stringToSplit, #pos+LEN(#delimiter),
LEN(#stringToSplit)-#pos)
END
INSERT INTO #returnList
SELECT #stringToSplit
RETURN
END
To apply this to your table, use CROSS APPLY (Single Delimiter):
SELECT mt.Name, x.Name AS ProductCode
FROM MyTable mt
CROSS APPLY dbo.splitstring(mt.Name, '_') x
WHERE ISNUMERIC(x.Name) = 1 AND LEN(x.Name) = 3
Update, Multiple Delimiters
I guess the real underlying problem is that ultimately the product codes need to be normalized out of the composite key (e.g. add a distinct ProductId or ProductCode column to the same table), derived using a query like this, and then stored back in the table via an update. Reverse engineering the product codes out of the string appears to be a trial and error process.
Nonetheless, you can continue to keep passing the split strings through further splitting functions (one per each type of delimiter), before applying your final discriminating filter:
SELECT *
FROM MyTable mt
CROSS APPLY dbo.splitstring(mt.Name, 'test') y -- First alias
CROSS APPLY dbo.splitstring(y.Name, '_') x -- Reference the preceding alias
WHERE ISNUMERIC(x.Name) = 1 AND LEN(x.Name) = 3; -- Must reference the last alias (x)
Note that the stringsplit function has again been changed to accommodate multicharacter delimiters.

Answer 3

If you have a table (or can generate in inline view) of the product codes, you can join the list of long strings to the product codes with a like clause.
Create Table longcodes (
longcode varchar(20)
)
Create Table products (
prodCode char(3)
)
insert products values('100')
insert products values('111')
insert products values('123')
insert longcodes values ('abc_a_100_test')
insert longcodes values ('asdf_111_bob')
insert longcodes values ('in_0314_123_95pf')
insert longcodes values ('f_100_u')
insert longcodes values ('hihi_111_bye')
insert longcodes values ('in_123_0314_95pf')
insert longcodes values ('a_b__c_d_100_efg')
select *
from products p
join longcodes l on l.longcode like '%_' + p.prodCode + '_%'
And they get aligned with the product codes like this:
prodCode longcode
100 abc_a_100_test
100 f_100_u
100 a_b__c_d_100_efg
111 asdf_111_bob
111 hihi_111_bye
123 in_0314_123_95pf
123 in_123_0314_95pf
EDIT: Seeing the developments in the other answer, you can simplify the like clause to
like p.prodCode
and just deal with the fact that you have a much greater chance of a single composite string producing multiple matches.