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Oracle foreign key constraint syntax. Oracle allows you to create, add, drop, disable, and enable a foreign key constraint. Create a foreign key constraint. The following statement illustrates the syntax of creating a foreign key constraint when you create a table: CREATE TABLE child_table ( ... CONSTRAINT fk_name FOREIGN KEY (col1, col2,...)
A foreign key constraint (also called a referential integrity constraint) designates a column as the foreign key and establishes a relationship between that foreign key and a specified primary or unique key, called the referenced key.
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.
19 mar 2019 · I'm trying to find a query which will return me a list of the foreign keys for a table and the tables and columns they reference. I am half way there with. SELECT a.table_name, a.column_name, a.constraint_name, c.owner FROM ALL_CONS_COLUMNS A, ALL_CONSTRAINTS C where A.CONSTRAINT_NAME = C.CONSTRAINT_NAME and a.table_name=:TableName and C.
23 maj 2017 · I'm looking for a query allowing to retrieve foreign key infos (each line: referrencing table & field, referrenced table & field) of an entire schema. I'm currently working on it and may end up with a solution in the next minutes/hours.
Learn how to create, alter, drop and enable/disable foreign key constraints in Oracle SQL with examples. Also, see how to add cascade delete, cascade set null and cascade update options to foreign key constraints.
We understand that indexing foreign keys will solve the table level locking issue especially during update/delete the primary key value from the parent table apart from improving the query performance in certain conditions. Our application team has created a primary key constraint on all the foreign key columns instead of an index.
