Sql Not Exist

The following SQL Server Not Exists query will find the Employees whose Occupation is neither Skilled Manual nor Clerical.

SELECT 
	E1.EmpID
       ,E1.Name
       ,E1.Occupation
FROM 
	Employee E1
WHERE NOT EXISTS
	( 
    		SELECT 
			* 
		FROM 
			Employee E2 
		WHERE 
			E1.EmpID = E2.EmpID 
			AND 
			Occupation IN ('Skilled Manual', 'Clerical')
	)

Note: Using NOT EXISTS may have a performance hit. Try to use LEFT JOIN and WHERE column is NULL to test if there is a performance improvement. Sometimes, NOT EXISTS may be faster, and sometimes it may be slower.

	SELECT 
		TOP (1000) *
	FROM 
	dbo.tbTable01 T1  (NOLOCK)
	INNER JOIN dbo.tbTable02 T2  (NOLOCK) ON T2.Id  = T1.Id
	--LEFT JOIN tbTable03 T3  (NOLOCK) ON T3.PlateId = T1.PlateId
	--WHERE T3.BiImagePlateId IS NULL
	WHERE 
		NOT EXISTS(SELECT TOP 1 1 FROM tbTable03 WHERE PlateId = T1.PlateId)
	ORDER BY 
		T2.TrxnTime

Sources:

https://www.tutorialgateway.org/sql-not-exists-operator/