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To declare foreign keys in PGSQL, there are few points which user should bear in mind: If you receive PostgreSQL Error likes ERROR: there is no unique constraint matching given keys for referenced table "xxxx", it is caused by failure on creating Foreign Keys.

If you specify a SET NULL action, make sure that you have not declared the columns in the child table as NOT NULL.įor more details on Foreign Key Constraints, please visit.

The foreign key name must be unique within the database.

The length of string types need not be the same.

The size and the sign of integer types has to be the same.

The two key fields must have the compatible field type.

InnoDB needs indexes on foreign keys and referenced keys so that foreign key checks can be fast and not require a table scan.

Index prefixes on foreign key columns are not supported.

In the referenced table, there must be an index where the referenced columns are listed as the first columns in the same order.

To declare foreign keys in MySQL, there are few points which user should bear in mind:

If you use "On Delete Set Null" but the field doesn't allow null.

If the two fields (Field name and the Foreign Field name) are using incompatible field type.

These errors are related to MySQL itself. There are some possible cases that might cause failure on creating Foreign Keys on MySQL database.

If you receive MySQL Error likes 1005: Can't create table '.\mydb\#sql-44c_1c.frm'(errno: 150), it is caused by failure on creating Foreign Keys. Why I cannot successfully create the foreign keys?Īpply Navicat Product: Navicat for MySQL, Navicat for PostgreSQL