Syntax

Single-table syntax:

UPDATE [LOW_PRIORITY] [IGNORE] table_reference 
  [PARTITION (partition_list)]
  SET col1={expr1|DEFAULT} [,col2={expr2|DEFAULT}] ...
  [WHERE where_condition]
  [ORDER BY ...]
  [LIMIT row_count]

Multiple-table syntax:

UPDATE [LOW_PRIORITY] [IGNORE] table_references
    SET col1={expr1|DEFAULT} [, col2={expr2|DEFAULT}] ...
    [WHERE where_condition]

Description

For the single-table syntax, the UPDATE statement updates columns of existing rows in the named table with new values. The SET clause indicates which columns to modify and the values they should be given. Each value can be given as an expression, or the keyword DEFAULT to set a column explicitly to its default value. The WHERE clause, if given, specifies the conditions that identify which rows to update. With no WHERE clause, all rows are updated. If the ORDER BY clause is specified, the rows are updated in the order that is specified. The LIMIT clause places a limit on the number of rows that can be updated.

MariaDB starting with 10.0

The PARTITION clause was introduced in MariaDB 10.0. See Partition Pruning and Selection for details.

Until MariaDB 10.3.2, for the multiple-table syntax, UPDATE updates rows in each table named in table_references that satisfy the conditions. In this case, ORDER BY and LIMIT cannot be used. This restriction was lifted in MariaDB 10.3.2 and both clauses can be used with multiple-table updates. An UPDATE can also reference tables which are located in different databases; see Identifier Qualifiers for the syntax.

where_condition is an expression that evaluates to true for each row to be updated.

table_references and where_condition are as specified as described in SELECT.

Assignments are evaluated in left-to-right order, unless the SIMULTANEOUS_ASSIGNMENT sql_mode (available from MariaDB 10.3.5) is set, in which case the UPDATE statement evaluates all assignments simultaneously.

You need the UPDATE privilege only for columns referenced in an UPDATE that are actually updated. You need only the SELECT privilege for any columns that are read but not modified. See GRANT.

The UPDATE statement supports the following modifiers:

  • If you use the LOW_PRIORITY keyword, execution of the UPDATE is delayed until no other clients are reading from the table. This affects only storage engines that use only table-level locking (MyISAM, MEMORY, MERGE). See HIGH_PRIORITY and LOW_PRIORITY clauses for details.
  • If you use the IGNORE keyword, the update statement does not abort even if errors occur during the update. Rows for which duplicate-key conflicts occur are not updated. Rows for which columns are updated to values that would cause data conversion errors are updated to the closest valid values instead.

UPDATE Statements With the Same Source and Target

MariaDB starting with 10.3.2

From MariaDB 10.3.2, UPDATE statements may have the same source and target.

For example, given the following table:

DROP TABLE t1;
CREATE TABLE t1 (c1 INT, c2 INT);
INSERT INTO t1 VALUES (10,10), (20,20);

Until MariaDB 10.3.1, the following UPDATE statement would not work:

UPDATE t1 SET c1=c1+1 WHERE c2=(SELECT MAX(c2) FROM t1);
ERROR 1093 (HY000): Table 't1' is specified twice, 
  both as a target for 'UPDATE' and as a separate source for data

From MariaDB 10.3.2, the statement executes successfully:

UPDATE t1 SET c1=c1+1 WHERE c2=(SELECT MAX(c2) FROM t1);

SELECT * FROM t1;
+------+------+
| c1   | c2   |
+------+------+
|   10 |   10 |
|   21 |   20 |
+------+------+

Example

Single-table syntax:

UPDATE table_name SET column1 = value1, column2 = value2 WHERE id=100;

Multiple-table syntax:

UPDATE tab1, tab2 SET tab1.column1 = value1, tab1.column2 = value2 WHERE tab1.id = tab2.id;

See Also

Comments

Comments loading...