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UPDATE Statement

The UPDATE statement modifies the values of rows in a table.

Examples

For every row where i is NULL, set the value to 0 instead:

UPDATE tbl
SET i = 0
WHERE i IS NULL;

Set all values of i to 1 and all values of j to 2:

UPDATE tbl
SET i = 1, j = 2;

Syntax

UPDATE changes the values of the specified columns in all rows that satisfy the condition. Only the columns to be modified need be mentioned in the SET clause; columns not explicitly modified retain their previous values.

Update from Other Table

A table can be updated based upon values from another table. This can be done by specifying a table in a FROM clause, or using a sub-select statement. Both approaches have the benefit of completing the UPDATE operation in bulk for increased performance.

CREATE OR REPLACE TABLE original AS
    SELECT 1 AS key, 'original value' AS value
    UNION ALL
    SELECT 2 AS key, 'original value 2' AS value;

CREATE OR REPLACE TABLE new AS
    SELECT 1 AS key, 'new value' AS value
    UNION ALL
    SELECT 2 AS key, 'new value 2' AS value;

SELECT *
FROM original;
key value
1 original value
2 original value 2 
UPDATE original
    SET value = new.value
    FROM new
    WHERE original.key = new.key;

Or:

UPDATE original
    SET value = (
        SELECT
            new.value
        FROM new
        WHERE original.key = new.key
    );

SELECT *
FROM original;
key value
1 new value
2 new value 2

Update from Same Table

The only difference between this case and the above is that a different table alias must be specified on both the target table and the source table. In this example AS true_original and AS new are both required.

UPDATE original AS true_original
    SET value = (
        SELECT
            new.value || ' a change!' AS value
        FROM original AS new
        WHERE true_original.key = new.key
    );

Update Using Joins

To select the rows to update, UPDATE statements can use the FROM clause and express joins via the WHERE clause. For example:

CREATE TABLE city (name VARCHAR, revenue BIGINT, country_code VARCHAR);
CREATE TABLE country (code VARCHAR, name VARCHAR);
INSERT INTO city VALUES ('Paris', 700, 'FR'), ('Lyon', 200, 'FR'), ('Brussels', 400, 'BE');
INSERT INTO country VALUES ('FR', 'France'), ('BE', 'Belgium');

To increase the revenue of all cities in France, join the city and the country tables, and filter on the latter:

UPDATE city
SET revenue = revenue + 100
FROM country
WHERE city.country_code = country.code
  AND country.name = 'France';

SELECT *
FROM city;
name revenue country_code
Paris 800 FR
Lyon 300 FR
Brussels 400 BE

Upsert (Insert or Update)

See the Insert documentation for details.

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