How Can Multi-Column RETURNING Enhance PostgreSQL Inserts Across Multiple Tables?

Utilizing Multi-Column RETURNING for Efficient PostgreSQL Inserts

In the world of data management, the ability to perform multiple inserts with a single RETURNING clause can streamline operations and enhance efficiency. This article delves into the intricacies of multi-insert operations with PostgreSQL 9.3, showcasing how to seamlessly insert data into multiple child tables while retrieving the newly generated ID.

The scenario involves three tables:

• table1 (parent): user_id, username, name, surname, emp_date
• table2 (child of table1): pass_id, user_id, password
• table3 (child of table1): user_dt_id, user_id, adress, city, phone

The task at hand is to insert data into table1 and simultaneously populate the user_id columns in table2 and table3 with the newly generated user_id.

To accomplish this, we employ data-modifying Common Table Expressions (CTEs). CTEs allow us to combine multiple SQL statements into a single unit, streamlining the insertion process. Here's a detailed breakdown of the CTE implementation:

WITH ins1 AS (  -- Insert into 'table1'
   INSERT INTO table1 (username, name, surname)
   VALUES ('johnee', 'john', 'smith')
   RETURNING user_id
   ),
ins2 AS (  -- Insert into 'table2' with 'user_id' from 'ins1'
   INSERT INTO table2 (user_id, password)
   SELECT ins1.user_id, 'secret'
   FROM ins1  -- No need to return anything here
   )
INSERT INTO table3 (user_id, adress, city, phone)  -- Insert into 'table3' with 'user_id' from 'ins1'
SELECT ins1.user_id, ...
FROM ins1
RETURNING user_id;

Key implementation details:

• A column definition list for INSERT statements is recommended to avoid potential issues stemming from changes in table structure.
• Redundant DEFAULT values are omitted, allowing for a concise and efficient code.
• The final RETURNING clause retrieves the user_id from the last INSERT operation, which typically aligns with the user_id from table3.

In summary, using multi-insert with RETURNING in PostgreSQL allows for a single batch insertion across multiple tables, reducing complexity and optimizing performance. Data-modifying CTEs provide a convenient means to achieve this, offering a highly reliable and efficient solution for complex data insertion workflows.

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