This topic describes incompatibilities between MySQL databases and MySQL tenants of OceanBase Database when you change the type of a constrained column. The incompatibilities vary depending on the constraint.
Note
In the following tables, an empty cell in the type column indicates that the type is not supported by the corresponding constraint. A hyphen (-) means N/A. 'All' means all types.
Change the type of a PRIMARY KEY column
The following table describes the types to which you can change a PRIMARY KEY column by executing the ALTER TABLE table_name MODIFY/CHANGE COLUMN DDL statement in a MySQL database and a MySQL tenant of OceanBase Database.
Column type in a MySQL database |
Supported target type |
Column type in a MySQL tenant of OceanBase Database |
Supported target type |
|---|---|---|---|
| INT | All | INTEGER | - |
| TINYINT | All | TINYINT | BOOLEAN |
| SMALLINT | All | SMALLINT | - |
| MEDIUMINT | All | MEDIUMINT | - |
| BIGINT | All | BIGINT | - |
| BOOL | All | BOOLEAN | TINYINT |
| DECIMAL | All | DECIMAL | - |
| NUMERIC | All | NUMERIC | - |
| REAL | All | FLOAT | - |
| DOUBLE | All | DOUBLE | - |
| FLOAT | All | FLOAT | - |
| BIT | All | BIT | - |
| CHAR | All | CHAR | - |
| NCHAR | All | CHAR | - |
| VARCHAR | All | VARCHAR | - |
| BINARY | All | BINARY | - |
| VARBINARY | All | VARBINARY | - |
| LONG VARBINARY | All | ||
| YEAR | All | YEAR | - |
| DATE | All | DATE | - |
| TIME | All | TIME | - |
| TIMESTAMP | All | TIMESTAMP | - |
| DATETIME | All | DATETIME | - |
| TINYBLOB | All | ||
| MEDIUMBLOB | All | ||
| BLOB | All | ||
| LONGBLOB | All | ||
| TINYTEXT | All | ||
| MEDIUMTEXT | All | ||
| TEXT | All | ||
| LONGTEXT | All | ||
| ENUM | All | ENUM | - |
| SET | All | SET | - |
| JSON | All |
Change the type of a UNIQUE KEY column
If a UNIQUE KEY column is of a type described in the preceding table, the types to which you can change the column by executing the ALTER TABLE table_name MODIFY/CHANGE COLUMN DDL statement in a MySQL database and a MySQL tenant of OceanBase Database are the same as those for a PRIMARY KEY column.
Change the type of a KEY column
If a KEY column is of a type described in the preceding table, the types to which you can change the column by executing the ALTER TABLE table_name MODIFY/CHANGE COLUMN DDL statement in a MySQL database and a MySQL tenant of OceanBase Database are the same as those for a PRIMARY KEY column.
Change the type of a FOREIGN KEY column
If a FOREIGN KEY column is of a type described in the preceding table, the types to which you can change the column by executing the ALTER TABLE table_name MODIFY/CHANGE COLUMN DDL statement in a MySQL database and a MySQL tenant of OceanBase Database are the same as those for a PRIMARY KEY column.
Change the type of a FULLTEXT-indexed column
The following table describes the types to which you can change a FULLTEXT indexed column by executing the ALTER TABLE table_name MODIFY/CHANGE COLUMN DDL statement in a MySQL database and a MySQL tenant of OceanBase Database.
Column type in a MySQL database |
Supported target type |
Column type in a MySQL tenant of OceanBase Database |
Supported target type |
|---|---|---|---|
| CHAR | All | CHAR | - |
| VARCHAR | All | VARCHAR | - |
| TINYTEXT | All | TINYTEXT | - |
| MEDIUMTEXT | All | MEDIUMTEXT | - |
| TEXT | All | TEXT | - |
| LONGTEXT | All | LONGTEXT | - |
| BINARY | - | ||
| VARBINARY | - | ||
| NCHAR | All | CHAR | - |
| JSON | All |