Basics Updated November 2026

UPDATE

UPDATE table SET col = value WHERE condition changes col in every row that matches the condition: UPDATE products SET price = price * 1.1 WHERE category = 'Drinks' raises drink prices by 10 percent. Without WHERE every row in the table is updated, so always check the WHERE with a SELECT first.

Syntax

UPDATE table SET column1 = value1 [, column2 = value2] [FROM other] WHERE condition;

Examples

UPDATE orders SET status = 'shipped' WHERE id = 42;

Result: 1 row updated

UPDATE products SET price = price * 1.10, updated_at = CURRENT_DATE WHERE category = 'Drinks';

Result: All drink prices raised 10 percent, with the date stamped

The right side can reference the column's current value.

UPDATE customers
SET total_spent = t.spent
FROM (SELECT customer_id, SUM(amount) AS spent FROM orders GROUP BY customer_id) AS t
WHERE t.customer_id = customers.id;

Result: Each customer's total copied from the orders table

UPDATE ... FROM works in PostgreSQL and SQLite 3.33+. MySQL uses UPDATE a JOIN b SET ... instead.

Common mistakes

Running UPDATE without WHERE changes every row; run SELECT COUNT(*) FROM table WHERE ... with the same condition first, or wrap the update in a transaction.
Using WHERE col = NULL to target missing values updates nothing; use IS NULL.
Separating SET assignments with AND instead of commas (SET a = 1 AND b = 2) is parsed as one boolean expression: SQLite sets a to 0 or 1 and PostgreSQL raises a type error.

Practice it

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Questions

How do I update one table using values from another?

PostgreSQL and SQLite: UPDATE a SET col = b.col FROM b WHERE b.id = a.id. Alternatively use a correlated subquery: SET col = (SELECT col FROM b WHERE b.id = a.id).

Can I undo an UPDATE?

Only if it ran inside a transaction that has not been committed: BEGIN; UPDATE ...; check; then COMMIT or ROLLBACK. After COMMIT you need a backup.

INSERT INTOINSERT INTO adds rows to a table. Syntax with a column list, inserting multiple rows in one statement, INSERT ... SELECT to copy data, RETURNING the new id.
DELETEDELETE FROM table WHERE condition removes matching rows. Delete by id, by subquery, duplicates, everything in a table, and DELETE versus TRUNCATE.
WHEREUse WHERE to keep only the rows that match a condition: equals, greater than, text matches, NULL checks, and combinations with AND, OR and NOT.
CASE WHENCASE WHEN returns different values depending on conditions. Label rows, bucket numbers into ranges, pivot with SUM(CASE ...), sort custom orders, handle NULL.