However in SQLite a view can not be used to add, update or delete the records in the underlying tables.ĬREATE VIEW view_name AS select_statement ĬREATE TEMPORARY VIEW database_name. > DELETE from ReqDetail WHERE ReqDetail.ReqNumber = OLD.ReqNumber Ī VIEW is a saved SELECT statement that can be used in much the same way as a table. > THEN RAISE(ABORT, 'update on table ReqDetail violates foreign key')ĭelete records from a child table when a record from the parent table is deletedĭELETE FROM child_table WHERE child_table. >WHERE ReqEquip.ReqNumber= NEW.ReqNumber) ISNULL) > WHEN ((SELECT ReqEquip.ReqNumber FROM ReqEquip Sqlite>CREATE TRIGGER ReqNumUp BEFORE UPDATE ON ReqDetail FOR EACH ROW BEGIN SQL error: This Requisition number does not exist in the ReqEquip table.ĬREATE TRIGGER trigger_name BEFORE UPDATE ON child_table FOR EACH ROW BEGIN Sqlite> insert into ReqDetail(ReqNumber,StockNumber,Quantity)values(2000,51001,15) > THEN RAISE(ABORT, 'This Requisition number does not exist in the ReqEquip table.') > WHEN ((SELECT ReqEquip.ReqNumber FROM ReqEquip WHERE ReqEquip.ReqNumber= NEW.ReqNumber) ISNULL) Sqlite> CREATE TRIGGER ReqNumIn BEFORE INSERT ON ReqDetail BEGIN primary_key FROM parent_table WHERE parent_table. Using Triggers to Enforce Referential IntegrityĬREATE TRIGGER trigger_name BEFORE INSERT ON child_table BEGIN Sqlite> select StockNumber,OnHandQuan,Descrip from inventory where StockNumber =75149 ħ5149|89|Ball Point Pens Blue Fine tip, 12pack Sqlite> INSERT INTO ReqDetail(ReqNumber,StockNumber,Quantity,ItemCost) VALUES(1003,75149,3,0.77) > WHERE inventory.StockNumber = NEW.StockNumber > UPDATE inventory SET OnHandQuan = (OnHandQuan- NEW.Quantity) Sqlite> CREATE TRIGGER inventoryupdate AFTER INSERT ON ReqDetail BEGIN Sqlite> select StockNumber,OnHandQuan,Descrip from inventory where StockNumber = 75149 ħ5149|92|Ball Point Pens Blue Fine tip, 12pack UPDATE inventory SET OnHandQuan = ( OnHandQuan - NEW.Quantity) WHERE inventory.StockNumber = NEW.StockNumber This trigger automatically updates the inventory table by subtracting the Quantity of items requisitioned from the OnHandQuan value when an insert statement adds a record to the ReqDetail table.ĬREATE TRIGGER inventoryupdate AFTER INSERT ON ReqDetail BEGIN Once created, triggers cannot be modified, to make changes the trigger must be dropped and then recreated. Triggers are deleted when the table that they are associated with is dropped or they can be deleted with a DROP TRIGGER statement. Each trigger must have a name that is unique to the database. In this case, the bio only applies to artist ID 8 so we'll null all rows where the ArtistId is not equal to 8.What is a trigger? In SQL, a trigger is a sql statement or series of sql statements that are executed automatically in response to a specified event such as the update of or creation or deletion of a table or record. We can set that column to NULL for all artists that this bio doesn't apply to. Oops! I don't think all these bands are Australian jazz bands centred around polyrhythms. The Wiggles Australian jazz band centred around polyrhythms. Mothers of Invention Australian jazz band centred around polyrhythms. Pat Metheny Australian jazz band centred around polyrhythms.įrank Gambale Australian jazz band centred around polyrhythms. Primus Australian jazz band centred around polyrhythms. Slayer Australian jazz band centred around polyrhythms. Strapping Young Lad Australian jazz band centred around polyrhythms. Magnum Australian jazz band centred around polyrhythms. Ian Moss Australian jazz band centred around polyrhythms. Iron Maiden Australian jazz band centred around polyrhythms.Ītmasphere Australian jazz band centred around polyrhythms. Mr Percival Australian jazz band centred around polyrhythms. Wayne Jury Australian jazz band centred around polyrhythms. Noiseworks Australian jazz band centred around polyrhythms. The Tea Party Australian jazz band centred around polyrhythms. Steve Vai Australian jazz band centred around polyrhythms. Joe Satriani Australian jazz band centred around polyrhythms. Sqlite> SELECT ArtistName, Bio FROM Artists SET Bio = 'Australian jazz band centred around polyrhythms.'
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