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sql-statement-update.md

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UPDATE | TiDB SQL Statement Reference
An overview of the usage of UPDATE for the TiDB database.
/docs/dev/sql-statements/sql-statement-update/
/docs/dev/reference/sql/statements/update/

UPDATE

The UPDATE statement is used to modify data in a specified table.

Synopsis

UpdateStmt ::=
    "UPDATE" UpdateOption
(   TableRef "SET" Assignment ("," Assignment)* WhereClause? OrderBy? Limit?
|   TableRefs "SET" Assignment ("," Assignment)* WhereClause?
)

UpdateOption ::=
    OptimizerHints? ("LOW_PRIORITY" | "HIGH_PRIORITY" | "DELAYED")? "IGNORE"?

TableRef ::=
    ( TableFactor | JoinTable )

TableRefs ::=
    EscapedTableRef ("," EscapedTableRef)*

Examples

mysql> CREATE TABLE t1 (id INT NOT NULL PRIMARY KEY AUTO_INCREMENT, c1 INT NOT NULL);
Query OK, 0 rows affected (0.11 sec)

mysql> INSERT INTO t1 (c1) VALUES (1), (2), (3);
Query OK, 3 rows affected (0.02 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM t1;
+----+----+
| id | c1 |
+----+----+
|  1 |  1 |
|  2 |  2 |
|  3 |  3 |
+----+----+
3 rows in set (0.00 sec)

mysql> UPDATE t1 SET c1=5 WHERE c1=3;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT * FROM t1;
+----+----+
| id | c1 |
+----+----+
|  1 |  1 |
|  2 |  2 |
|  3 |  5 |
+----+----+
3 rows in set (0.00 sec)

MySQL compatibility

TiDB always uses the original value of a column when evaluating expressions. For example:

CREATE TABLE t (a int, b int);
INSERT INTO t VALUES (1,2);
UPDATE t SET a = a+1,b=a;

In MySQL, the column b is updated to 2 because it is set to the value of a, and the value of a (which is 1) is updated to a+1 (which is 2) in the same statement.

TiDB follows the more standard SQL behavior, and updates b to 1.

See also