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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.
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.
The syntax to drop a foreign key in Oracle/PLSQL is: ALTER TABLE table_name. DROP CONSTRAINT constraint_name; Example. If you had created a foreign key as follows: CREATE TABLE supplier. ( supplier_id numeric(10) not null, supplier_name varchar2(50) not null, contact_name varchar2(50), CONSTRAINT supplier_pk PRIMARY KEY (supplier_id) );
The DROP CONSTRAINT command is used to delete a UNIQUE, PRIMARY KEY, FOREIGN KEY, or CHECK constraint. DROP a UNIQUE Constraint. To drop a UNIQUE constraint, use the following SQL: SQL Server / Oracle / MS Access: ALTER TABLE Persons DROP CONSTRAINT UC_Person; MySQL: ALTER TABLE Persons DROP INDEX UC_Person; DROP a PRIMARY KEY Constraint.
To delete a foreign key from a table, use the ALTER TABLE clause with the name of the table (in our example, student) followed by the clause DROP CONSTRAINT with the name of the foreign key constraint. In our example, the name of this constraint is fk_student_city_id.
A solution to fix this problem is to use the Oracle foreign key constraint to enforce the relationship between rows from the supplier_groups and suppliers tables. First, drop the suppliers table: DROPTABLE suppliers; Code language:SQL (Structured Query Language)(sql) Second, recreate the suppliers table with a foreign key constraint:
You cannot drop a table whose primary key is being referenced by a foreign key even if the foreign key constraint is in DISABLE NOVALIDATE state. Further, the optimizer can use constraints in DISABLE NOVALIDATE state.
