Optional Parameters for Update
Hello all,
I am building an ASP application which will update a SQL Server database.
The app will, at various times, update several different fields within the same table. For example, if I am updating a customers table, I may need to update only address one time, and only phone number another time, and still yet other times, I may need to update all fields in the table. It seems like I shouldn't have to write separate stored procedures for each of these instances. How can I write my stored procedure such that I can update a variable number of fields each time it is called.
I am building an ASP application which will update a SQL Server database.
The app will, at various times, update several different fields within the same table. For example, if I am updating a customers table, I may need to update only address one time, and only phone number another time, and still yet other times, I may need to update all fields in the table. It seems like I shouldn't have to write separate stored procedures for each of these instances. How can I write my stored procedure such that I can update a variable number of fields each time it is called.
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There is no performance gain by using stored procedure vs. executing the dynamic sql as the SQL server caches last few queries irrespctive of its origin. Stored procedure are also cached in the same way as any other dynamic query and so they have no advantage performance wise.
You can have optional parameter in stored procedures and do what you are asking but that only complicates the code and spreads business logic in 2 places instead of one. That is a maintanace overhead. Unless you or your company has a standard of writing all queries in stored procedure, there is no need for writing stored procedures for simple queries like one line select, update and inserts.
If you still feel that you need to write a stored procedure we can tell you how to use optional parameters.
You can have optional parameter in stored procedures and do what you are asking but that only complicates the code and spreads business logic in 2 places instead of one. That is a maintanace overhead. Unless you or your company has a standard of writing all queries in stored procedure, there is no need for writing stored procedures for simple queries like one line select, update and inserts.
If you still feel that you need to write a stored procedure we can tell you how to use optional parameters.
ASKER
I'm working with an existing application in which all other db opps are done using stored procedures.
Amit G is absolutely right!
Here is an example.
sSQL = ""
sSQL = sSQL + " Update MyTable "
sSQL = sSQL + " Set My_id = " + CStr(aMyId) + ", "
sSQL = sSQL + " Status = 'Test.' "
sSQL = sSQL + " Where (Status = 'A') "
objConn1.BeginTrans
objConn1.Execute sSQL
objConn1.CommitTrans
But the easiest way to to update all fields all the time if possible. It would be easier to maintain such code that way.
Even if you do that using strored proc, pass a value to all input parameters all time. But within proc update fields where the corresponding input variables are not null.
This way you have only one proc.
Here is an example.
sSQL = ""
sSQL = sSQL + " Update MyTable "
sSQL = sSQL + " Set My_id = " + CStr(aMyId) + ", "
sSQL = sSQL + " Status = 'Test.' "
sSQL = sSQL + " Where (Status = 'A') "
objConn1.BeginTrans
objConn1.Execute sSQL
objConn1.CommitTrans
But the easiest way to to update all fields all the time if possible. It would be easier to maintain such code that way.
Even if you do that using strored proc, pass a value to all input parameters all time. But within proc update fields where the corresponding input variables are not null.
This way you have only one proc.
Ok. Here is how you can create a stored procedure with optional parameters ...
CREATE PROCEDURE MyStoredProcedure
@first int = NULL
,@second int = NULL
,@third int = 0
AS
...
...
...
You can give a null value or a predetermined value to any parameter that you make an optional parameter. Later in the logic you can check if the parameter has the default value (say null) and that means it was not passed by the caller. To call these stored procedure from the client you can use ADO's Command object with or without Parameters. For example you could call the aboove stored procedure as
cmd.CommandText = "MyStoredProcedure"
cmd.CommandType = adCmdStoredProc
cmd.Parameters.Append cmd.CreateParameter("@seco
cmd.Parameters("param1") = Whatever
cmd.Execute
This way you have passed only second parameter. You can also call this in this way ...
cmd.CommandText = "exec MyStoredProcedure @second = " & Whatever
cmd.Execute
CREATE PROCEDURE MyStoredProcedure
@first int = NULL
,@second int = NULL
,@third int = 0
AS
...
...
...
You can give a null value or a predetermined value to any parameter that you make an optional parameter. Later in the logic you can check if the parameter has the default value (say null) and that means it was not passed by the caller. To call these stored procedure from the client you can use ADO's Command object with or without Parameters. For example you could call the aboove stored procedure as
cmd.CommandText = "MyStoredProcedure"
cmd.CommandType = adCmdStoredProc
cmd.Parameters.Append cmd.CreateParameter("@seco
cmd.Parameters("param1") = Whatever
cmd.Execute
This way you have passed only second parameter. You can also call this in this way ...
cmd.CommandText = "exec MyStoredProcedure @second = " & Whatever
cmd.Execute
ASKER
Thanks! Let me review and try this out, I'll post as to how it goes.
Also, when you get a chance please maintain yur old open questions:
1 09/02/2003 250 Email a "Fillable" PDF Open JavaScript
2 08/07/2003 125 Unable to open registry key Open Active Server Pages (ASP)
3 09/14/2003 250 NVidia Video Card only 16 colors Open Windows ME
4 10/02/2003 500 Implicit conversion from data type varch... Open Microsoft SQL Server
Thanks,
Anthony
1 09/02/2003 250 Email a "Fillable" PDF Open JavaScript
2 08/07/2003 125 Unable to open registry key Open Active Server Pages (ASP)
3 09/14/2003 250 NVidia Video Card only 16 colors Open Windows ME
4 10/02/2003 500 Implicit conversion from data type varch... Open Microsoft SQL Server
Thanks,
Anthony
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Would you need further help? If not, please close this issue. :)
Regards.
Regards.
ASKER
Ok. I'll close it today.
ASKER
I'm splitting the points because this project was scuttled and I never got a chance to fully implement these solutions. I am picking the "right" answer based upon tests that I did at the time of this post.
ASKER
Amit_g's original answer turned out to be the best solution. It is best to make the dynamic SQL statement in your ASP code, but in this particular application, I was extending functionality of an established app. This app made strict use of keeping queries in Stored Procedures and not ASP. I felt that it was best to continue this with the extension that I was working on.
Thanks all for the comments.
Thanks all for the comments.
ASKER