SQL Keywords

What this page is

This is a practical keyword index for fast recall. Syntax varies by database; examples are ANSI-style unless noted.

Query structure

• SELECT – choose columns/expressions
• FROM – source tables/views/subqueries
• WHERE – row filtering (before grouping)
• GROUP BY – group rows for aggregates
• HAVING – filter groups (after grouping)
• ORDER BY – sort result
• LIMIT/TOP/FETCH – restrict row count (vendor-specific)

Joins

• JOIN/INNER JOIN – matching rows only
• LEFT JOIN – keep all left rows, match right when possible
• RIGHT JOIN – keep all right rows (less common)
• FULL OUTER JOIN – keep both sides (not in MySQL; use UNION workaround)
• CROSS JOIN – cartesian product

SELECT o.id, c.name
FROM orders o
JOIN customers c ON c.id = o.customer_id
WHERE o.status = 'paid';

Filtering and predicates

• AND, OR, NOT – boolean logic
• IN – membership check
• BETWEEN – inclusive range
• LIKE – pattern match (%, _)
• IS NULL/IS NOT NULL – null checks
• EXISTS – subquery existence

SELECT *
FROM products
WHERE price BETWEEN 10 AND 50
  AND name LIKE '%pro%'
  AND discontinued IS NULL;

Aggregation

• COUNT, SUM, AVG, MIN, MAX – aggregate functions
• DISTINCT – unique values

SELECT customer_id, COUNT(*) AS order_count
FROM orders
GROUP BY customer_id
HAVING COUNT(*) >= 5
ORDER BY order_count DESC;

Set operations

• UNION – merge distinct rows
• UNION ALL – merge including duplicates
• INTERSECT – common rows (vendor-specific)
• EXCEPT/MINUS – rows in first but not second (vendor-specific)

Subqueries and derived tables

• AS – alias
• WITH – common table expression (CTE)

WITH recent AS (
  SELECT id, customer_id
  FROM orders
  WHERE created_at >= '2026-01-01'
)
SELECT customer_id, COUNT(*) AS n
FROM recent
GROUP BY customer_id;

DDL (schema)

• CREATE, ALTER, DROP – create/change/remove objects
• TABLE, VIEW, INDEX, DATABASE – object types
• PRIMARY KEY, FOREIGN KEY, UNIQUE, CHECK – constraints
• DEFAULT, NOT NULL – column rules

CREATE TABLE users (
  id INT PRIMARY KEY,
  email VARCHAR(255) UNIQUE NOT NULL,
  created_at DATETIME DEFAULT CURRENT_TIMESTAMP
);

DML (data changes)

• INSERT – add rows
• UPDATE – modify rows
• DELETE – remove rows

UPDATE users
SET email = 'new@example.com'
WHERE id = 10;

Transactions

• BEGIN/START TRANSACTION
• COMMIT
• ROLLBACK
• SAVEPOINT

START TRANSACTION;
UPDATE accounts SET balance = balance - 50 WHERE id = 1;
UPDATE accounts SET balance = balance + 50 WHERE id = 2;
COMMIT;

Handy notes

• WHERE vs HAVING: WHERE filters rows; HAVING filters groups.
• NULL is not equal to anything (even another NULL). Use IS NULL.
• Join condition belongs in ON; row filters belong in WHERE (most of the time).