UPDATE

Updates rows in the specified table.

Syntax

UPDATE <table_name> SET <column1> = <expression1> [, <column2> = <expression2> ...] WHERE <condition>

Parameter	Description
`<table_name>`	The table to update rows in.
`<column>`	The name of the column to be updated.
`<expression>`	An expression which computes a new value to populate the column. The expression can reference any column from the row being updated.
`<condition>`	A Boolean expression. Only rows for which this expression returns `true` will be updated. Condition can have subqueries doing semijoin with other table(s).

Remarks

Updated rows are marked for deletion, but are not automatically cleaned up. You can monitor fragmentation in information_schema.tables to understand how many rows are marked for deletion out of total rows; fragmentation = (rows marked for deletion / total rows). Total row count in information_schema.tables excludes the number of rows marked for deletion. Query performance is not materially impacted by delete marks.

To mitigate fragmentation, use the VACUUM command to manually clean up deleted rows.

Example with WHERE

This example applies a discount for products which have excessive inventory.

UPDATE product SET price = price * 0.9 WHERE quantity > 10

Table before:

product
+------------+--------+----------+
| name       | price  | quantity |
+---------------------+----------+
| wand       |    120 |        9 |
| broomstick |    270 |       15 |
| robe       |     80 |        1 |
| cauldron   |     20 |      112 |
+------------+--------+----------+

Table after:

product
+------------+--------+----------+
| name       | price  | quantity |
+---------------------+----------+
| wand       |    120 |        9 |
| broomstick |    243 |       15 |
| robe       |     80 |        1 |
| cauldron   |     18 |      112 |
+------------+--------+----------+

Example updating multiple columns

This example applies a discount and updates the quantity of a specific product.

UPDATE product SET price = 15, quantity = 100 WHERE name = 'quaffle'

Table before:

product
+------------+--------+----------+
| name       | price  | quantity |
+---------------------+----------+
| wand       |    120 |        9 |
| broomstick |    270 |       15 |
| quaffle    |        |          |
| robe       |     80 |        1 |
| cauldron   |     20 |      112 |
+------------+--------+----------+

Table after:

product
+------------+--------+----------+
| name       | price  | quantity |
+---------------------+----------+
| wand       |    120 |        9 |
| broomstick |    270 |       15 |
| quaffle    |     15 |      100 |
| robe       |     80 |        1 |
| cauldron   |     20 |      112 |
+------------+--------+----------+

Known limitations

Below are some known limitations of the UPDATE command.

Only one UPDATE will be executed against a table at once.
UPDATE cannot be used on tables that have certain aggregating indexes An attempt to issue a UPDATE statement on a table with a join index or aggregating index outside of the below defined will fail - these table level aggregating indexes need to be dropped first. UPDATE can be used on tables that have aggregating indexes containing the following aggregating functions, starting in DB version 3.16.0: