Such constraints are implemented with unique indexes in PostgreSQL. The referenced columns in the target table must have a primary key or unique constraint. In the following, I will call the table, on which the foreign key constraint is defined, the source table and the referenced table the target table. This article will explain that and show you how to search for missing indexes. Any help is much appreciated.Foreign key index performance © Laurenz Albe 2018įoreign key constraints are an important tool to keep your database consistent while also documenting relationships between tables.Ī fact that is often ignored is that foreign keys need proper indexing to perform well. Please provide some examples and explain to me like I'm five. Then, I want to put ISLNo in my 'Hourly' table. That being said, if I'm required to put EmpNo and ProgramSupervisorNo in my 'ISL' table, how am I to put the ISLNo in my 'Hourly' table?Ĭlear as mud? Basically, I just to put ProgramSupervisorNo in the 'ISL' table because each ISL has a ProgramSupervisor. Doesn't this violate normalization standards? Since it requires both EmpNo and ProgramSupervisorNo in the 'ISL' table, doesn't this mean that ProgramSupervisorNo relies on EmpNo and therefore one of the fields shouldn't be included? I'm new to this so please forgive my shoddy explanations.Īlso, 'Hourly' employees belong to one ISL and ISL's can have numerous 'Hourly' employees, but the 'Hourly' table is also a child table of Employee and has EmpNo as its primary key. When I create the 'ISL' table, in order to reference the composite 'ProgramSupervisor' PK as a FK in the ISL table, Access requires both PK field names. However, I also want ProgramSupervisorNo to be a PK of the 'ProgramSupervisor' table and have a composite PK for it. I have a ProgramSupervisor table that's a child table of the 'Salary' parent table and 'Salary' is a child table of the parent table 'Employee.' With the PK of 'Employee' being EmpNo, the PK of Salary and then ProgramSupervisor are also EmpNo. First off, the ERD is a little misleading. Now that you have the info, let me explain the problem I'm having. Here's the ERD and the relationships I'm striving for: How do I clear out all the references to the foreign key after the key with the foreign record has been deleted so I can save the deletion of the primary key record to the database?įirst off, here's my code for the three tables I'm having problems with: CREATE TABLE ProgramSupervisorĬONSTRAINT PKProgramSupervisor PRIMARY KEY (EmpNo, ProgramSupervisorNo) ,ĬONSTRAINT FKProgSupEmpNo FOREIGN KEY (EmpNo) REFERENCES Employee )ĬONSTRAINT FKISLProgSupNo FOREIGN KEY (ProgramSupervisorNo, EmpNo)ĬONSTRAINT FKEmpNo FOREIGN KEY (EmpNo) REFERENCES Employee,ĬONSTRAINT FKISLNo FOREIGN KEY (ISLNo) REFERENCES ISL ) The SaveData function is just the standard save with a refilling of the table, but the change to the datatable can't be saved to the database because there are still references to the Foreign Key. () īindingNavigatorDeleteItem.Enabled = true īizDocStartupDBDataSet1.EnforceConstraints = true OldEmployeeTitlesRow = (currentPersonID,1) bizDocStartupDBDataSet1.EnforceConstraints = false īizDocStartupDBDataSet1.EmployeeTitlesRow oldEmployeeTitlesRow This is the portion where I perform the deletes. Trying to do it with only the Cascade Delete without the code got the same error. I tried editing the foreign key constraint to do a Cascade Delete and it still gives the same error. After doing it through code failed I tried changing the EnforceConstraints to False in the DataSet Designer View. Īccording to what I've seen online I should be able to disable the EnforceConstraints either through code or through the DataSet Designer View. Instead it gives the following error:Įrror: The primary key value cannot be deleted because references to this key still exist. When I perform a delete on a primary key record it deletes the foreign key record and saves the change, but when it goes to delete the primary key record it won't let me save the deletion of the primary key record to the database.
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