How to create fast database queries

Archive for June 23rd, 2009

IN with a comma separated list: SQL Server

with 2 comments

From Stack Overflow:

How do I search a table for all values from a comma separated list, or return all values if the list contains a single 0?

Using comma separated lists in SQL Server as a search parameter is generally considered a bad design and should be avoided.

One should pass lists in a table variable rather than in a set of comma separated values.

However, there are legacy applications, ORM's and these kinds of stuff that just leave you no choice.

MySQL provides a nice function find_in_set designed exactly for this task.

SQL Server does not directly support an IN predicate for CSV, neither it provides find_in_set. It needs a rowset for IN predicate to work.

To expand a comma separated list into a rowset, we will use a recursive CTE.

In the CTE, we should search for the position of every next comma and return it.

Then we can just take the substring between two commas and cast it into an INT:

SET @lid = '3, 14, 15, 296, 5358';
WITH    cd AS
        SELECT  1 AS first, CHARINDEX(',', @lid, 1) AS next
        UNION ALL
        SELECT  next + 1, CHARINDEX(',', @lid, next + 1)
        FROM    cd
        WHERE   next > 0
        lid AS
        SELECT  CAST(SUBSTRING(@lid, first, CASE next WHEN 0 THEN LEN(@lid) + 1 ELSE next END - first)AS INT) AS id
        FROM    cd
FROM    lid

Now we just need to return the values from the table found in this list, or all values if there is a single 0 in the list.

Let's create a sample table and build a query to do this:
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Written by Quassnoi

June 23rd, 2009 at 11:00 pm

Posted in SQL Server