This topic describes incompatibilities between MySQL databases and MySQL tenants of OceanBase Database when you change the length 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, and a hyphen (-) means N/A.
Change the length of a PRIMARY KEY column
The following table describes the operations that you can perform to change the length of 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 | Allowed operation | Column type in a MySQL tenant of OceanBase Database | Allowed operation |
|---|---|---|---|
| INT | Increase and decrease the length | INTEGER | Increase and decrease the length |
| TINYINT | Increase and decrease the length | TINYINT | Increase and decrease the length |
| SMALLINT | Increase and decrease the length | SMALLINT | Increase and decrease the length |
| MEDIUMINT | Increase and decrease the length | MEDIUMINT | Increase and decrease the length |
| BIGINT | Increase and decrease the length | BIGINT | Increase and decrease the length |
| BOOL | - | BOOLEAN | - |
| DECIMAL | Increase and decrease the length | DECIMAL | Increase the length |
| NUMERIC | Increase and decrease the length | NUMERIC | Increase the length |
| REAL | Increase and decrease the length | FLOAT | Increase and decrease the length |
| DOUBLE | Increase and decrease the length | DOUBLE | Increase and decrease the length |
| FLOAT | Increase and decrease the length | FLOAT | Increase and decrease the length |
| BIT | Increase and decrease the length | BIT | Increase and decrease the length |
| CHAR | Increase and decrease the length | CHAR | Increase the length |
| NCHAR | Increase and decrease the length | CHAR | Increase the length |
| VARCHAR | Increase and decrease the length | VARCHAR | Increase the length |
| BINARY | Increase and decrease the length | BINARY | - |
| VARBINARY | Increase and decrease the length | VARBINARY | Increase the length |
| LONG VARBINARY | - | ||
| YEAR | Increase and decrease the length | YEAR | Increase the length (the length is fixed to be 4 bytes) |
| DATE | - | DATE | - |
| TIME | Increase and decrease the length | TIME | Increase the length |
| TIMESTAMP | Increase and decrease the length | TIMESTAMP | Increase the length |
| DATETIME | Increase and decrease the length | DATETIME | Increase the length |
| TINYBLOB | - | ||
| MEDIUMBLOB | - | ||
| BLOB | - | ||
| LONGBLOB | - | ||
| TINYTEXT | - | ||
| MEDIUMTEXT | - | ||
| TEXT | - | ||
| LONGTEXT | - | ||
| ENUM | Increase and decrease the length | ENUM | Increase the length |
| SET | Increase and decrease the length | SET | Increase the length |
| JSON | - |
Change the length of a UNIQUE KEY column
If a UNIQUE KEY column is of a type described in the preceding table, the operations that you can perform to change the column length 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 length of a KEY column
If a KEY column is of a type described in the preceding table, the operations that you can perform to change the column length 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 length of a FOREIGN KEY column
The following table describes the operations that you can perform to change the length of a FOREIGN 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 | Allowed operation | Column type in a MySQL tenant of OceanBase Database | Allowed operation |
|---|---|---|---|
| INT | Increase and decrease the length | INTEGER | Increase and decrease the length |
| TINYINT | Increase and decrease the length | TINYINT | Increase and decrease the length |
| SMALLINT | Increase and decrease the length | SMALLINT | Increase and decrease the length |
| MEDIUMINT | Increase and decrease the length | MEDIUMINT | Increase and decrease the length |
| BIGINT | Increase and decrease the length | BIGINT | Increase and decrease the length |
| BOOL | - | BOOLEAN | - |
| DECIMAL | - | DECIMAL | Increase the length |
| NUMERIC | - | NUMERIC | Increase the length |
| REAL | Increase and decrease the length | FLOAT | Increase and decrease the length |
| DOUBLE | Increase and decrease the length | DOUBLE | Increase and decrease the length |
| FLOAT | Increase and decrease the length | FLOAT | Increase and decrease the length |
| BIT | - | BIT | Increase and decrease the length |
| CHAR | - | CHAR | Increase the length |
| NCHAR | - | CHAR | Increase the length |
| VARCHAR | Increase the length | VARCHAR | Increase the length |
| BINARY | - | BINARY | - |
| VARBINARY | Increase the length | VARBINARY | Increase the length |
| LONG VARBINARY | - | ||
| YEAR | - | YEAR | Increase the length (the length is fixed to be 4 bytes) |
| DATE | - | DATE | - |
| TIME | - | TIME | Increase the length |
| TIMESTAMP | - | TIMESTAMP | Increase the length |
| DATETIME | - | DATETIME | Increase the length |
| TINYBLOB | - | ||
| MEDIUMBLOB | - | ||
| BLOB | - | ||
| LONGBLOB | - | ||
| TINYTEXT | - | ||
| MEDIUMTEXT | - | ||
| TEXT | - | ||
| LONGTEXT | - | ||
| ENUM | Increase the length | ENUM | Increase the length |
| SET | Increase the length | SET | Increase the length |
| JSON | - |
Change the length of a FULLTEXT-indexed column
The following table describes the operations that you can perform to change the length of 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 | Allowed operation | Column type in a MySQL tenant of OceanBase Database | Allowed operation |
|---|---|---|---|
| CHAR | Increase and decrease the length | CHAR | - |
| VARCHAR | Increase and decrease the length | VARCHAR | - |
| TINYTEXT | - | TINYTEXT | - |
| MEDIUMTEXT | - | MEDIUMTEXT | - |
| TEXT | - | TEXT | - |
| LONGTEXT | - | LONGTEXT | - |
| BINARY | - | ||
| VARBINARY | - | ||
| NCHAR | Increase and decrease the length | CHAR | - |
| JSON | - |
