How to Find Foreign Key Relationships for a Given Table in SQL?

Use SQL to retrieve foreign key information of a table

Understanding the foreign keys associated with a specific table is critical to maintaining data integrity and understanding relationships in the database. Here's how to retrieve foreign key information using SQL:

information_schema Database provides insight into database metadata, including foreign key relationships. You can leverage the table_constraints, key_column_usage and constraint_column_usage tables to extract the information you need.

To list all foreign keys for a given table, you can use the following query:

<code class="language-sql">SELECT
    tc.table_schema, 
    tc.constraint_name, 
    tc.table_name, 
    kcu.column_name, 
    ccu.table_schema AS foreign_table_schema,
    ccu.table_name AS foreign_table_name,
    ccu.column_name AS foreign_column_name 
FROM information_schema.table_constraints AS tc 
JOIN information_schema.key_column_usage AS kcu
    ON tc.constraint_name = kcu.constraint_name
    AND tc.table_schema = kcu.table_schema
JOIN information_schema.constraint_column_usage AS ccu
    ON ccu.constraint_name = tc.constraint_name
WHERE tc.constraint_type = 'FOREIGN KEY'
    AND tc.table_schema='<table_schema>'
    AND tc.table_name='<table_name>';</code>

Replace <table_schema> and <table_name> with the actual schema and table for which you want to retrieve foreign key information.

If you need to determine which table to use as a foreign table, modify the last two conditions in the query as follows:

<code class="language-sql">    AND ccu.table_schema='<table_schema>'
    AND ccu.table_name='<table_name>';</code>

This query will give you a detailed list of all foreign keys for a given table and their associated information.

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