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ADD COLUMN
ADD INDEX
ADMIN
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ALTER DATABASE
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ANALYZE TABLE
BEGIN
CHANGE COLUMN
COMMIT
CREATE DATABASE
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CREATE TABLE LIKE
CREATE TABLE
CREATE USER
DEALLOCATE
DELETE
DESC
DESCRIBE
DO
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EXPLAIN ANALYZE
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GRANT <privileges>
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Important
You are viewing the documentation of an older version of the TiDB database (TiDB v2.1).
It is recommended that you use the latest LTS version of the TiDB database.
MODIFY COLUMN
The ALTER TABLE.. MODIFY COLUMN
statement modifies a column on an existing table. The modification can include changing the data type and attributes. To rename at the same time, use the CHANGE COLUMN
statement instead.
Synopsis
AlterTableStmt:
AlterTableSpec:
ColumnKeywordOpt:
ColumnDef:
ColumnPosition:
Examples
mysql> CREATE TABLE t1 (id int not null primary key AUTO_INCREMENT, col1 INT);
Query OK, 0 rows affected (0.11 sec)
mysql> INSERT INTO t1 (col1) VALUES (1),(2),(3),(4),(5);
Query OK, 5 rows affected (0.02 sec)
Records: 5 Duplicates: 0 Warnings: 0
mysql> ALTER TABLE t1 MODIFY col1 BIGINT;
Query OK, 0 rows affected (0.09 sec)
mysql> SHOW CREATE TABLE t1\G
*************************** 1. row ***************************
Table: t1
Create Table: CREATE TABLE `t1` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`col1` bigint(20) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin AUTO_INCREMENT=30001
1 row in set (0.00 sec)
mysql> ALTER TABLE t1 MODIFY col1 INT;
ERROR 1105 (HY000): unsupported modify column length 11 is less than origin 20
mysql> ALTER TABLE t1 MODIFY col1 BLOB;
ERROR 1105 (HY000): unsupported modify column type 252 not match origin 8
mysql> ALTER TABLE t1 MODIFY col1 BIGINT, MODIFY id BIGINT NOT NULL;
ERROR 1105 (HY000): can't run multi schema change
MySQL compatibility
- Making multiple changes in a single
ALTER TABLE
statement is not currently supported. - Only certain types of data type changes are supported. For example, an
INTEGER
toBIGINT
is supported, but the reverse is not possible. Changing from an integer to a string format or blob is not supported. - Modifying precision of the
DECIMAL
data type is not supported.
See also
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