How to find who uses MariaDB in PostgreSQL

How do I find customers who bought MariaDB products in PostgreSQL?

Retrieve a list of customers that have purchased MariaDB-related products by joining Customers, Orders, OrderItems, and Products.

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Description

Why ask “who uses MariaDB” in a PostgreSQL database?

Teams often migrate from MariaDB or sell MariaDB-based services. Knowing which customers interact with MariaDB products helps target migrations, upsells, or support.

How do I build the core query?

Join Customers → Orders → OrderItems → Products and filter on product names that contain ‘MariaDB’. Use DISTINCT to avoid duplicates.

Step 1: Locate MariaDB product IDs

SELECT id FROM Products WHERE name ILIKE '%mariadb%';

Step 2: Join tables to reach customers

SELECT DISTINCT c.* FROM Customers c JOIN Orders o ON o.customer_id = c.id JOIN OrderItems oi ON oi.order_id = o.id JOIN Products p ON p.id = oi.product_id WHERE p.name ILIKE '%mariadb%';

How can I improve performance?

Create B-tree indexes on Products.name, Orders.customer_id, and OrderItems.order_id to speed up the joins and LIKE filter.

What are best practices?

1) Use ILIKE for case-insensitive matches.
2) Qualify columns to avoid ambiguity.
3) SELECT only needed columns in production.

Common mistakes and fixes

Duplicates: Forgetting DISTINCT returns the same customer many times. Add DISTINCT or aggregate.
Slow scans: Missing indexes causes sequential scans. Index frequently filtered columns.

Can I encapsulate this in a view?

Yes. CREATE OR REPLACE VIEW maria_db_customers AS (/* core query */); lets analysts query SELECT * FROM maria_db_customers;.

How do I refresh the list regularly?

Schedule the query in Galaxy or a cron-driven psql script. Store results in a reporting table if historical tracking is required.

Why How to find who uses MariaDB in PostgreSQL is important

How to find who uses MariaDB in PostgreSQL Example Usage


-- List each customer and the total they spent on MariaDB products
SELECT c.id,
       c.name,
       SUM(o.total_amount) AS mariadb_spend
FROM   Customers   c
JOIN   Orders      o  ON o.customer_id = c.id
JOIN   OrderItems  oi ON oi.order_id   = o.id
JOIN   Products    p  ON p.id          = oi.product_id
WHERE  p.name ILIKE '%MariaDB%'
GROUP  BY c.id, c.name
ORDER  BY mariadb_spend DESC;

How to find who uses MariaDB in PostgreSQL Syntax


SELECT DISTINCT c.id, c.name, c.email, c.created_at
FROM   Customers   AS c
JOIN   Orders      AS o  ON o.customer_id = c.id
JOIN   OrderItems  AS oi ON oi.order_id   = o.id
JOIN   Products    AS p  ON p.id          = oi.product_id
WHERE  p.name ILIKE '%MariaDB%';

Common Mistakes

Using SELECT * without DISTINCT returns duplicate customer rows because each order item creates an extra row. Fix: add DISTINCT or aggregate results.
Filtering with LOWER(name) LIKE '%mariadb%' prevents index use. Fix: apply ILIKE with a trigram or dedicated functional index for faster searches.