Select All Or One With A Single Query
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Very often, you'll have the need to select either everything from a table or just a single record. This is the way to do both given a single query. When @EmployeeID is NULL, it will return all records from Employee, when a value is present, it will return only the value that is present.
-- Use one query to select a record given an identifier or all records when that ID is NULL declare @EmployeeID int set @EmployeeID = 42 -- NULL select * from Employee where EmployeeID = coalesce(@EmployeeID, EmployeeID)
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