Question

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Parameterizing a SQL IN clause?

Hi, I have a query looks like this:

SELECT 
    CompanyId 
FROM 
    CompanyTable 
WHERE 
    CompanyName IN ('Subway', 'A & W', 'Pizzahut')

Is there any way I can use sql parameters for the names list?

This is not a stored proc (which I prefer but can’t use in this project). When I say ‘parameter’, I mean parameter in the parametrized inline sql.

I use MS Enterprise Library so my parametrized inline sql looks like this:

string sql = "SELECT * FROM Company WHERE CompanyID = @companyId";
Database db = DatabaseFactory.CreateDatabase();
DbCommand dbCommand = db.GetSqlStringCommand(sql);
db.AddInParameter(dbCommand, "companyId", DbType.Int32, 123);
...

It is pretty straightforward for simple cases like above. But when it comes to something like

SELECT 
    CompanyId 
FROM 
    CompanyTable 
WHERE 
    CompanyName IN ('Subway','A & W','Pizzahut').

I have no idea how to use parameters here.

Answer 1

There are a few routes that you can take

• The “classic” pass in a delimited string parameter and use a user defined table-valued function in the database to turn the string into a table. Then you can join on that table to filter.

Something like (this will return a table of INT datatypes, just change the code slightly for VARCHAR

CREATE function [dbo].[csl_to_table] ( @list nvarchar(MAX) )
RETURNS @list_table TABLE ([id] INT)
AS
BEGIN
    DECLARE     @index INT,
                @start_index INT,
                @id INT

    SELECT @index = 1 
    SELECT @start_index = 1
    WHILE @index <= DATALENGTH(@list)
    BEGIN

        IF SUBSTRING(@list,@index,1) = ','
        BEGIN

                SELECT @id = CAST(SUBSTRING(@list, @start_index, 
                        @index - @start_index ) AS INT)
                INSERT @list_table ([id]) VALUES (@id)
                SELECT @start_index = @index + 1
        END
        SELECT @index  = @index + 1
    END
    SELECT @id = CAST(SUBSTRING(@list, @start_index, 
            @index - @start_index ) AS INT)
    INSERT @list_table ([id]) VALUES (@id)
    RETURN
END

• You can use a loop in your .NET code to build the IN clause. Remember however that you are limited to 256 parameters (IIRC).

Something like this (a la this answer)

string[] tags = new string[] { "Subway","A & W","Pizzahut" };
string cmdText = 
    "SELECT CompanyId FROM CompanyTable WHERE CompanyName IN ({0})";

string[] paramNames = tags.Select(
    (s, i) => "@tag" + i.ToString()
).ToArray();

string inClause = string.Join(",", paramNames);
using (SqlCommand cmd = new SqlCommand(string.Format(cmdText, inClause))) {
    for(int i = 0; i < paramNames.Length; i++) {
       cmd.Parameters.AddWithValue(paramNames[i], tags[i]);
    }
}

• Depending on the version of SQL, could use an XML DataType Parameter (SQL Server 2005 onwards) to pass multiple parameters or a Table-Valued Parameter (SQL Server 2008 onwards)