COALESCE is new function in SQL Server 2005. This is used to create comma-separated value string i.e to create the same resultset with a single SELECT statement. The following code shows how it's done.
DECLARE @EmployeeList varchar(100)
SELECT @EmployeeList = COALESCE(@EmployeeList + ', ', '') +
CAST(Emp_UniqueID AS varchar(5))
FROM SalesCallsEmployees
WHERE SalCal_UniqueID = 1
SELECT @EmployeeList
--Results--
---------
1, 2, 4, 5
The COALESCE function performs the magic here. When @EmployeeList is NULL (the first row processed), it returns an empty string. On subsequent rows, it concatenates the @EmployeeList value with a comma and the current @Emp_UniqueID value.
Performance of the SQL MERGE vs. INSERT/UPDATE
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MERGE is designed to apply both UPDATE and INSERTs into a target table from
a source table. The statement can do both at once, or simply do INSERTs or
on...
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