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ALTER TABLE Room ADD FOREIGN KEY (RoomType_ID) REFERENCES RoomType(RoomType_ID), ADD FOREIGN KEY (Reservation_ID) REFERENCES Reservation(Reservation_ID), ADD FOREIGN KEY (Gust_ID) REFERENCES Gust(Gust_ID);
Add a foreign key constraint to a table. If you want to add a foreign key constraint to an existing table, you use the ALTER TABLE statement as follows: ALTER TABLE child_table ADD CONSTRAINT fk_name FOREIGN KEY (col1,col2) REFERENCES parent_table(col1,col2); Code language: SQL (Structured Query Language) (sql) Drop a foreign key constraint
18 lip 2013 · alter table tab1. add c1 number(20) constraint tab1_c1_fk references tab2(c2); c1 new column in the table tab1 with the FK tab1_c1_fk on the table tab2 column c2. At least as of 11, constraint constraint_name isn't strictly necessary. It could just be add c1 number(20) references tab2(c2).
This Oracle tutorial explains how to use Foreign Keys in Oracle with syntax and examples. A foreign key is a way to enforce referential integrity within your Oracle database. A foreign key means that values in one table must also appear in another table.
Next, add foreign keys (optional). A foreign key establishes a relationship between a column (or columns) in one table and a primary or unique key in another table.
Tables can declarative specify relationships between tables, typically referred to as referential integrity. To see how this works we can create a "child" table of the DEPARTMENTS table by including a foreign key in the EMPLOYEES table that references the DEPARTMENTS table. For example:
Syntax. ALTER TABLE table_name ADD CONSTRAINT constraint_name FOREIGN KEY (column1, column2, ...) REFERENCES parent_table (column1, column2, ... Example: Let’s add foreign key constraint in Students table using this query: ALTER TABLE students ADD CONSTRAINT fk_teacher FOREIGN KEY (teacher_id) REFERENCES teachers (teacher_id) Drop Foreign Key.
