Chapter 30: PostgreSQL AS
the AS keyword (and its very frequent optional version — no AS at all). Many beginners think “AS is just for renaming columns”, but it is actually much more powerful and appears in several...
Category: PostgreSQL
Chapter 31: PostgreSQL JOINS
PostgreSQL JOINs ☕🧩 You’ve already learned: CREATE TABLE, INSERT, SELECT, WHERE, GROUP BY, AVG, LIKE, IN, BETWEEN, AS… Now we reach the real power of relational databases: combining data from multiple tables using JOIN....
Chapter 32: PostgreSQL INNER JOIN
The INNER JOIN. You’ve already learned basic SELECT, WHERE, LIKE, IN, BETWEEN, AS, and we just did a quick overview of all JOIN types. Today we go deep only into INNER JOIN — because...
Chapter 33: PostgreSQL LEFT JOIN
PostgreSQL LEFT JOIN ☕🛡️ Last time we covered INNER JOIN — which only shows matching rows from both tables. Today we go to LEFT JOIN — which says: “I want every single row from...
Chapter 34: PostgreSQL RIGHT JOIN
PostgreSQL RIGHT JOIN (also called RIGHT OUTER JOIN). You’ve already seen: INNER JOIN → only matching rows from both sides LEFT JOIN → all rows from left table + matching from right RIGHT JOIN...
Chapter 35: PostgreSQL FULL JOIN
PostgreSQL FULL JOIN INNER JOIN → only matching rows from both sides LEFT JOIN → all from left + matching from right RIGHT JOIN → all from right + matching from left Now we...
Chapter 36: PostgreSQL CROSS JOIN
PostgreSQL: CROSS JOIN. You’ve already seen INNER, LEFT, RIGHT, FULL — all of them try to match rows between two tables using some condition (ON or USING). CROSS JOIN does not match anything. It...
Chapter 37: PostgreSQL UNION Operator
Postgre UNION Operator (and its close cousins: UNION ALL, INTERSECT, EXCEPT). Grab your chai — it’s February 14, 2026, around 12:15 PM in Hyderabad ☕📊 Today we’re going to treat UNION like we’re combining...
Chapter 38: PostgreSQL GROUP BY Clause
The GROUP BY clause ☕📊 You already know: SELECT, WHERE, ORDER BY, LIMIT Aggregates like COUNT, SUM, AVG, MIN, MAX JOIN, UNION Now we reach GROUP BY — the command that says: “I don’t...
Chapter 39: PostgreSQL HAVING Clause
The HAVING clause. You already know: WHERE filters individual rows before grouping GROUP BY creates groups and lets you calculate aggregates per group (COUNT, AVG, SUM…) But what if you want to filter the...
