How to drop a FOREIGN KEY constraint only if it exists?

How to drop a FOREIGN KEY constraint only if it exists?

The more simple solution is provided in Eric Isaacs’s answer. However, it will find constraints on any table. If you want to target a foreign key constraint on a specific table, use this:

Can you add a foreign key in PostgreSQL?

I’m still new to postgreSQL. I have two tables I created that I want to go back and add Primary and Foreign key constraints for and no matter what I do I can’t seem to add a foreign key. Here’s what I have:

Do you know the name of the constraint?

James’s answer works just fine if you know the name of the actual constraint. The tricky thing is that in legacy and other real world scenarios you may not know what the constraint is called. If this is the case you risk creating duplicate constraints, to avoid you can use:

How to check foreign keys related to a table in MySQL?

How to check foreign keys related to a table Ask Question Asked6 years, 1 month ago Active1 year, 1 month ago Viewed121k times 55 20 How to see foreign keys related to a table in MySql? Background: I wanted to drop a table in MySql which has a foreign key constraint. When I do it I get this: Error Code: 1217.

Where do I find check constraint in SQL Server?

If you review the CHECK constraint definition in the previous CREATE TABLE statement, you will see that we have not mentioned the name of the defined constraint. In this case, SQL Server will assign a unique name for that constraint that can be shown by querying the INFORMATION_SCHEMA.TABLE_CONSTRAINTS system view for the ConstraintDemo4 table.

How to find the FK of a table?

I achieved the same thing with a slightly different method: You can use those queries to find all FKs for your table. Declare @SchemaName VarChar (200) = ‘Schema Name’ Declare @TableName VarChar (200) = ‘Table name’ — Find FK in This table.