Sql updating tables with foreign keys

It means that you can only insert a row into the child table if there is a corresponding row in the parent table.

To enforce this logic, we place a foreign key on the ORDERS table and have it reference the primary key of the CUSTOMER table.

If you want to avoid losing rows where you can't find a matching row in .

In addition to what I already listed under the prequel question: If the INSERT is huge and constitutes a large proportion of the target table, it is probably faster to DROP all indexes on the target table and recreate them afterwards.

Foreign Key A foreign key is a column (or columns) that references a column (most often the primary key) of another table.

The purpose of the foreign key is to ensure referential integrity of the data.

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