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How to populate foreign key values using sequences?
CREATE OR REPLACE TRIGGER orders_bir BEFORE INSERT ON orders FOR EACH ROW WHEN (new.id IS NULL) BEGIN SELECT orders_seq.NEXTVAL INTO :new.id FROM dual; END; / CREATE OR REPLACE TRIGGER order_lines_bir BEFORE INSERT ON order_lines FOR EACH ROW WHEN (new.id IS NULL) BEGIN SELECT order_lines_seq.NEXTVAL INTO :new.id FROM dual; END; /
How to insert values into two tables with a foreign key?
Table tblStaff with columns id (primary key, auto increment), name, age, address Table tblRoleOfStaff with columns id (primary key, auto increment), StaffId (foreign key to tblStaff ), RoleId
How to get the sequence value for the master record?
Another option is to query the sequence value before inserting the master record. This way you have the appropriate sequence value ready for the foreign key column in the detail record. DECLARE l_order_id orders.id%TYPE; BEGIN — Select the next sequence value.
How is IDENT _ CURRENT limited by scope and session?
IDENT_CURRENT is not limited by scope and session; it is limited to a specified table. IDENT_CURRENT returns the identity value generated for a specific table in any session and any scope. So you make take last scoped but not current one.
Is it possible to change the foreign key value?
This isn’t possible when the foreign key is part of the table’s primary key. SET DEFAULT: Replace the foreign key value with the column’s default value. CASCADE: Delete or update all foreign key rows. NO ACTION: On update, make no modifications of foreign key values. RESTRICT: Do not allow deletions of primary key rows.
What happens when a foreign key matches a primary key?
When a foreign key value matches a primary key value, we know that there is a logical relationship between the database objects represented by the matching rows. One of the major constraints on a relation is referential integrity, which states that every non-null foreign key must reference an existing primary key value.
Is there a limit to the number of foreign key references?
Greater than 253 foreign key references are not currently available for columnstore indexes, memory-optimized tables, Stretch Database, or partitioned foreign key tables. Unlike primary key constraints, creating a foreign key constraint does not automatically create a corresponding index.