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Multiple parameters in a Select statement at run time

Posted on 2006-07-13
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Last Modified: 2010-04-16
What is the best way to format a Select statement when the amount of parameter variables are not known until run time?
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Question by:fly412s
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4 Comments
 
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Expert Comment

by:DarkXiphoid
ID: 17103039
Make an arraylist with parameters. Like this string[] paramList = new string[]

That way you can add any number of parameters during runtime.

Hope this helps you in the right direction.

Regards,

Robert
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LVL 25

Expert Comment

by:dstanley9
ID: 17103641
Are you talking about a SQL SELECT statement?  AFAIK it's not possible.  The best way I've seen is to use a finite set of VARCHAR parameters:

CREATE PROCEDURE MyParameterHack
@param1 VARCHAR(500) = null,
@param2 VARCHAR(500) = null,
@param3 VARCHAR(500) = null,
@param4 VARCHAR(500) = null,
@param5 VARCHAR(500) = null,
@param6 VARCHAR(500) = null
AS
...

However, SQL does support "optional" parameters, which may be a better option.

What is the procedure going to do?  Maybe there's an alternate method than variable parameters



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Author Comment

by:fly412s
ID: 17103700
I'm using ADO.net.  I'm using the System.Data.OleDb namespace.  I'm connecting to a flat database file (.csv).  
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Accepted Solution

by:
dstanley9 earned 500 total points
ID: 17103811
Then you can build it using string concatenation.

For example, to use a dynamic WHERE clause, use arrays for field names and values:

string[] fields;
string [] values;

// build arrays of fields and values

string sql = "SELECT * FROM flatfile WHERE " 
for(int i=0; i<numParams; i++)
{
  sql += "[" + fields[i] + "] = @Param" + i.ToString() ;
  if (i<numparams-1)
    sql += " AND ";
}
OleDbCommand command = new OleDbCommand(sql);

for(int i=0; i<numParams; i++)
{
  command.Parameters.Add("@Param" + i.ToString(),values[i]);
}



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