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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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Last modified: 2024-03-19