Even for the experienced iSeries guru, SQL's "exception join" syntax is rarely understood and even more rarely...
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Ironically, it's very similar to the (much more globally understood) "unmatched records with primary file" option in Query/400.
Consider the following two tables:
> select * from employee EMPLOYEEID EMPLOYEENAME DEPARTMENTID 1 Greg Graffin 1 2 Dino Cazares 2 3 Burton Bell 2 4 Lee Ving 4 5 Mike Levine 4 6 Devin Townsend 6 7 Otep Shamaya 7 > select * from department DEPARTMENTID DEPARTMENTNAME 1 HR 2 IS 3 QA 4 CR To find employees with an invalid department: > select Employee.employeeName from Employee exception join Department on Employee.departmentID = Department.departmentID EMPLOYEENAME Devin Townsend Otep Shamaya To find departments that contain no employees: > select Department.departmentName, Department.departmentID from Department exception join Employee on Employee.departmentID = Department.departmentID DEPARTMENTNAME DEPARTMENTID QA 3 The exception join is functionally equivalent to: SELECT Employee.employeeName FROM Employee where not exists (select * from Department where Employee.departmentID = Department.departmentID) or > select Employee.employeeName from Employee where Employee.departmentID not in (select departmentID from Department)
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