SQL Syntax Cheat Sheet: Joins, Clauses, and Common Functions

The single most useful fact on this sql cheat sheet: the order you write clauses in is not the order the database actually runs them in. That mismatch is exactly why WHEREcan't reference a SELECT alias but ORDER BY can — by the time ORDER BY runs, the alias already exists; by the time WHEREruns, it doesn't.

Same reasoning explains why HAVING filters on aggregates and WHEREcan't —WHERE runs before GROUP BY has produced any aggregates to filter on. Full clause precision and dialect-specific edge cases are covered in the SQL Formatter guide.

A LEFT JOIN silently turns into an INNER JOIN the moment a WHERE clause filters on a nullable right-side column — a bug common enough to have its own section in the EXPLAIN ANALYZE guide.

All five ignore NULL values except COUNT(*), which counts rows regardless of nulls — COUNT(col) counts only the non-null values of that column.

These names are not universal — this is the sql functions list most engines agree on closely enough to be useful, not a guarantee. Postgres also accepts || for concatenation alongside CONCAT(); SQL Server uses LEN() instead of LENGTH(); MySQL's CONCAT() tolerates NULL arguments where Postgres's || propagates them. Check your specific engine before assuming a name works everywhere.

Date functions vary more across engines than almost anything else in SQL — treat this table as a starting point for translating a query between dialects, not as syntax you can paste unchanged into any database.

SELECT column1, column2
FROM table_name
WHERE condition
GROUP BY column1
HAVING aggregate_condition
ORDER BY column1
LIMIT 10;

INSERT INTO table_name (column1, column2)
VALUES (value1, value2);

UPDATE table_name
SET column1 = value1
WHERE condition;

DELETE FROM table_name
WHERE condition;

An UPDATE or DELETE with no WHERE clause runs against every row in the table — worth a second look before you hit execute. Building these safely, with real placeholders instead of string-concatenated values, is what the parameterized query builder guide covers.

Writing correct SQL and writing SQL a reviewer can read in a pull request are two different jobs. Once a query works, running it through GenKitLab's SQL Formatter puts each clause on its own line and indents subqueries consistently for Postgres, MySQL or SQL Server — the same before/after transform covered in the SQL Formatter guide. It runs entirely in your browser, so nothing you paste is uploaded anywhere.