Dynamic SQL, sp_executesql, and rebuilding the dynamic sql statement - Part 1 - tsql

Question

Part 1: In his article, "Dynamic Search Conditions in T-SQL...for SQL 2005 and Earlier", Erland Sommarskog gives an example of how to use dynamic sql with sp_executesql.
http://www.sommarskog.se/dyn-search-2005.html#sp_executesql
SELECT #sql = -- 19
'SELECT o.OrderID, o.OrderDate, od.UnitPrice, od.Quantity, -- 20
c.CustomerID, c.CompanyName, c.Address, c.City, -- 21
c.Region, c.PostalCode, c.Country, c.Phone, -- 22
p.ProductID, p.ProductName, p.UnitsInStock, -- 23
p.UnitsOnOrder -- 24
FROM dbo.Orders o -- 25
JOIN dbo.[Order Details] od ON o.OrderID = od.OrderID -- 26
JOIN dbo.Customers c ON o.CustomerID = c.CustomerID -- 27
JOIN dbo.Products p ON p.ProductID = od.ProductID -- 28
WHERE 1 = 1' -- 29
-- 30
IF #orderid IS NOT NULL -- 31
SELECT #sql = #sql + ' AND o.OrderID = #xorderid' + -- 32
' AND od.OrderID = #xorderid' -- 33
-- 34
IF #fromdate IS NOT NULL -- 35
SELECT #sql = #sql + ' AND o.OrderDate >= #xfromdate' -- 36
etc...
So, as you build your dynamic sql statement, it makes sense if you have to run just one sp_executesql for your #sql variable.
However, let's suppose you've built your #sql, and returned the filtered records you want returned, but you also want a COUNT of the records returned.
What would be the best way to go about doing this?
Would you have to declare another variable, #sql_2, whose build would be nearly identical to #sql, except the SELECT statement in #sql_2 would do a SELECT COUNT(*)... instead of a SELECT col1, col2, col3?
Or is there a better approach to take?

Answer 1

String the SQL statements together separated by semicolons. Here is a working example that returns the tables in your database that start with the letter "A" and the count.
First the simple version. This returns 2 result sets, the second one being the count.
declare #findTables nvarchar(256)
set #findTables = N'A%'
declare #sql nvarchar(max)
set #sql = N'set nocount on; '+
'select * from sys.tables where name like '''+#findTables+''';'+
'select ##RowCount as [RowCount];';
execute sp_executesql #sql
Now a version where a variable gets valued with the count for when you need to use it later in the stored proc.
declare #findTables nvarchar(256)
set #findTables = N'A%'
declare #sql nvarchar(max)
declare #ParmDefinition nvarchar(500);
declare #rowCount int
set #sql = N'set nocount on;
select * from sys.tables where name like #findTablesParm;
select #rowCountParm = ##rowcount;
select #rowCountParm as [RowCount];';
SET #ParmDefinition = N'#findTablesParm nvarchar(256),
#rowCountParm int OUTPUT';
execute sp_executesql #sql,
#ParmDefinition,
#findTablesParm=#findTables,
#rowCountParm=#rowCount OUTPUT
After this runs you should see 2 result sets, the second one will contain the RowCount and the variable #rowCount will also contain the row count.