


Single-Query Data Insertion Across Multiple Related Postgres Tables
This guide addresses the challenge of inserting data into multiple interconnected Postgres tables using a single SQL query, specifically when needing to retrieve a primary key from an initial insertion and utilize it as a foreign key in subsequent insertions.
The Problem: Efficiently inserting data into three or more related tables within a single query, ensuring proper foreign key relationships are maintained.
Solution: Leveraging Data-Modifying CTEs
Common Table Expressions (CTEs) offer an elegant solution. Data-modifying CTEs allow sequential INSERT operations, where each subsequent insertion relies on the results of the preceding one.
Implementation Example:
The following demonstrates inserting data into three tables (sample
, sample1
, sample2
) using data-modifying CTEs:
WITH ins1 AS ( INSERT INTO sample(firstname, lastname) VALUES ('fai55', 'shaggk') RETURNING id AS sample_id ), ins2 AS ( INSERT INTO sample1 (sample_id, adddetails) SELECT sample_id, 'ss' FROM ins1 RETURNING user_id ) INSERT INTO sample2 (user_id, value) SELECT user_id, 'ss2' FROM ins2;
Explanation:
-
ins1
: Inserts a row into thesample
table and returns the newly generatedid
(primary key) assample_id
. -
ins2
: Utilizes thesample_id
fromins1
to insert a row intosample1
, returning the generateduser_id
. - Final
INSERT
: Employs theuser_id
fromins2
to insert data intosample2
.
Alternative: Batch Insertion with CTEs
This approach handles multiple data rows simultaneously:
WITH data(firstname, lastname, adddetails, value) AS ( VALUES ('fai55', 'shaggk', 'ss', 'ss2'), ('fai56', 'XXaggk', 'xx', 'xx2') ), ins1 AS ( INSERT INTO sample (firstname, lastname) SELECT firstname, lastname FROM data RETURNING firstname, lastname, id AS sample_id ), ins2 AS ( INSERT INTO sample1 (sample_id, adddetails) SELECT ins1.sample_id, d.adddetails FROM data d JOIN ins1 USING (firstname, lastname) RETURNING sample_id, user_id ) INSERT INTO sample2 (user_id, value) SELECT ins2.user_id, d.value FROM data d JOIN ins1 USING (firstname, lastname) JOIN ins2 USING (sample_id);
This efficiently inserts multiple rows by defining them within the data
CTE.
Important Considerations:
- Foreign Key Constraints: Ensure appropriate foreign key constraints are defined to maintain referential integrity.
-
ON CONFLICT Clause: Utilize
ON CONFLICT
to manage potential duplicate key errors. - Concurrency: Be mindful of potential race conditions during concurrent data writes.
This comprehensive approach provides a robust and efficient method for managing data insertion across related Postgres tables within a single query.
The above is the detailed content of How to Insert Data into Multiple Related Postgres Tables in a Single Query?. For more information, please follow other related articles on the PHP Chinese website!

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