comparing a column to a list of values in t-sql

Question

I have a situation where I am displaying records on a page, and I need a way for the user to select a subset of those records to be displayed on another page. These records aren't stored anywhere then, it is a dynamically generated thing. I know I could use jquery to pass in a comma-separated value to my other web page, but I'm not sure what is the best way to in sql say where uniqueid is in this list of ids not in a table etc. I know I could dynamically construct the sql with a bunch of ors, but that seems like a hack. anyone else have any suggestions?

Answer 1

You can use the solution Joel Spolsky recently gave for this problem.

SELECT * FROM MyTable
WHERE ',' + 'comma,separated,list,of,words' + ','
  LIKE '%,' + MyTable.word + ',%';

That solution is clever but slow. The better solution is to split the comma-separated string, and construct a dynamic SQL query with the IN() predicate, adding a query parameter placeholder for each element in your list of values:

SELECT * FROM MyTable
WHERE word IN ( ?, ?, ?, ?, ?, ?, ?, ? );

The number of placeholders is what you have to determine when you split your comma-separated string. Then pass one value from that list per parameter.

If you have too many values in the list and making a long IN() predicate is unwieldy, then insert the values to a temporary table, and JOIN against your main table:

CREATE TEMPORARY TABLE TempTableForSplitValues (word VARCHAR(20));

...split your comma-separated list and INSERT each value to a separate row...

SELECT * FROM MyTable JOIN TempTableForSplitValues USING (word);

Also see many other similar questions on SO, including:

• Dynamic SQL Comma Delimited Value Query
• Passing a varchar full of comma delimited values to a SQL Server IN function
• Parameterized Queries with Like and In
• Parameterizing a SQL IN clause?

Answer 2

this is the best source:

http://www.sommarskog.se/arrays-in-sql.html

create a split function, and use it like:

SELECT
    *
    FROM YourTable  y
    INNER JOIN dbo.splitFunction(@Parameter) s ON y.ID=s.Value

I prefer the number table approach

For this method to work, you need to do this one time table setup:

SELECT TOP 10000 IDENTITY(int,1,1) AS Number
    INTO Numbers
    FROM sys.objects s1
    CROSS JOIN sys.objects s2
ALTER TABLE Numbers ADD CONSTRAINT PK_Numbers PRIMARY KEY CLUSTERED (Number)

Once the Numbers table is set up, create this function:

CREATE FUNCTION [dbo].[FN_ListToTable]
(
     @SplitOn  char(1)      --REQUIRED, the character to split the @List string on
    ,@List     varchar(8000)--REQUIRED, the list to split apart
)
RETURNS TABLE
AS
RETURN 
(

    ----------------
    --SINGLE QUERY-- --this will not return empty rows
    ----------------
    SELECT
        ListValue
        FROM (SELECT
                  LTRIM(RTRIM(SUBSTRING(List2, number+1, CHARINDEX(@SplitOn, List2, number+1)-number - 1))) AS ListValue
                  FROM (
                           SELECT @SplitOn + @List + @SplitOn AS List2
                       ) AS dt
                      INNER JOIN Numbers n ON n.Number < LEN(dt.List2)
                  WHERE SUBSTRING(List2, number, 1) = @SplitOn
             ) dt2
        WHERE ListValue IS NOT NULL AND ListValue!=''

);
GO

You can now easily split a CSV string into a table and join on it:

select * from dbo.FN_ListToTable(',','1,2,3,,,4,5,6777,,,')

OUTPUT:

ListValue
-----------------------
1
2
3
4
5
6777

(6 row(s) affected)

Your can pass in a CSV string into a procedure and process only rows for the given IDs:

SELECT
    y.*
    FROM YourTable y
        INNER JOIN dbo.FN_ListToTable(',',@GivenCSV) s ON y.ID=s.ListValue