All Tools VerseSQL is the language for querying and changing data in relational databases. This cheat sheet covers the statements you use most, from basic queries to joins, aggregates, and updates.
Query basics
| Statement | What it does |
|---|---|
SELECT * FROM t |
Get all columns from a table |
SELECT a, b FROM t |
Get specific columns |
WHERE x = 1 |
Filter rows by a condition |
ORDER BY a DESC |
Sort results, descending |
LIMIT 10 |
Return only the first 10 rows |
SELECT DISTINCT a FROM t |
Remove duplicate values |
Filtering
| Operator | What it does |
|---|---|
a = 1 / a <> 1 |
Equal / not equal |
a IN (1,2,3) |
Matches any value in a list |
a BETWEEN 1 AND 9 |
Within a range |
a LIKE 'A%' |
Pattern match; % is any text |
a IS NULL |
Is empty (null) |
AND / OR |
Combine conditions |
Joins
| Join | What it does |
|---|---|
INNER JOIN |
Rows matching in both tables |
LEFT JOIN |
All left rows, matched right or null |
RIGHT JOIN |
All right rows, matched left or null |
FULL JOIN |
All rows from both sides |
ON a.id = b.id |
The condition that links the tables |
Aggregates
| Function | What it does |
|---|---|
COUNT(*) |
Count rows |
SUM(a) |
Add up a column |
AVG(a) |
Average of a column |
MIN(a) / MAX(a) |
Smallest / largest value |
GROUP BY a |
Group rows for aggregation |
HAVING COUNT(*) > 1 |
Filter groups after aggregating |
Modify data
| Statement | What it does |
|---|---|
INSERT INTO t (a) VALUES (1) |
Add a new row |
UPDATE t SET a = 1 WHERE id = 2 |
Change existing rows |
DELETE FROM t WHERE id = 2 |
Remove rows |
CREATE TABLE t (id INT, a TEXT) |
Create a table |
ALTER TABLE t ADD b INT |
Add a column |
DROP TABLE t |
Delete a table |
Frequently Asked Questions
What is SQL?
SQL, or Structured Query Language, is the standard language for reading and writing data in relational databases like MySQL, PostgreSQL, and SQLite.
What is the difference between WHERE and HAVING?
WHERE filters rows before grouping. HAVING filters groups after an aggregate like COUNT or SUM has been applied.
What is the difference between INNER and LEFT JOIN?
An inner join returns only rows that match in both tables. A left join returns all rows from the left table, with nulls where there is no match.
Is SQL the same in every database?
The core is standardized, so most queries are portable. Each database adds its own extensions and small differences in functions and types.
See our free developer tools for formatting and data work.