确定SQL Server查询（存储过程）结果类型

Question

I am planning to organize my data in SQL Server as a small orm of my own, creating classes of meta data on each in my code.

For the tests I am hard-coding the objects, the next step is to generate the properties of each using SQL Server queries about those objects.

And now that I deal with the stored procedures section of my code in C#,
I was wondering how it is possible to somehow use SQL Server to query the result type of the command executed?

For example, here we know what it's doing even by reading its name ...

[dbo].[GtallDrLFilesCount]

but another could select some other type of return such as rowset string etc'

Using the above stored procedure will return an int :

if(@AllDrives=1) Begin 
        Select 
          * From [dbo].[HddFolderFiles]
End

but the next (above) selects all content rather the RowsCount

I was planning to access SQL Server and query it's objects, and as I do not plan to set return parameter (OUT), is there a more elegant way to achieve it, rather than parsing the .sql file of the stored procedure?

Like if text contains SELECT * (this is a rowset) expect it with DataTable if text contains Select COUNT(*) (this is int) prepare int type variable.

I thought in the case I did not assign an out parameter to my stored procedures can SQL Server tell the return type somehow even though it has no out parameter to make it easy for it?

Answer 1

I think you would have to execute the SProc to get it's columns, but you could do it without actually returing data using set fmtonly

Even sprocs that return a single value (eg - int) return a table when you use c# ... so you just need to take a look at the reader's Columns to get the data you want.

So:

set fmtonly on
exec [dbo].[MyStoredProc] 0
set fmtonly off

Will return a recordset which you can examine in c#

var adoCon = new System.Data.SqlClient.SqlConnection(_sConnectStr);
var adoCmd = new System.Data.SqlClient.SqlCommand("your SQL (above)", adoCon);

var Rows = adoCmd.ExecuteReader();
DataTable dtSchema = Rows.GetSchemaTable();

Now - you can wander through dtSchema to get columns. It's not pure SQL, but it's ac# + SQL approach. [dbo].[GtallDrLFilesCount] will return a single column table (column of type int).

Obviously - use a SQL command (not string). The next trick is translating SQL types into native c# types (easy for some data types and tricky for others ... take a look at ADOCommand's ReturnProviderSpecificTypes option).

Hope that helps!

Answer 2

From SQL Server 2012+ you can use sys.dm_exec_describe_first_result_set to read metadata about resultset:

This dynamic management function takes a Transact-SQL statement as a parameter and describes the metadata of the first result set for the statement.

SELECT *
FROM sys.dm_exec_describe_first_result_set(
   N'EXEC [dbo].[MyProcedure]', NULL, 0);

SELECT *
FROM sys.dm_exec_describe_first_result_set(
   N'SELECT * FROM [dbo].[tab]', NULL, 0);

SqlFiddleDemo

This method has limitation for more info read Remarks section