This topic describes the supported conversion scope of CREATE TABLE DDL operations for creating columns during data migration from a MySQL database to a MySQL-compatible tenant of OceanBase Database.
Syntax
create_definition:
col_name column_definition
column_definition: {
data_type [NOT NULL | NULL] [DEFAULT {literal | (expr)} ]
[VISIBLE | INVISIBLE]
[AUTO_INCREMENT] [UNIQUE [KEY]] [[PRIMARY] KEY]
[COMMENT 'string']
[COLLATE collation_name]
[COLUMN_FORMAT {FIXED | DYNAMIC | DEFAULT}]
[ENGINE_ATTRIBUTE [=] 'string']
[SECONDARY_ENGINE_ATTRIBUTE [=] 'string']
[STORAGE {DISK | MEMORY}]
[reference_definition]
[check_constraint_definition]
| data_type
[COLLATE collation_name]
[GENERATED ALWAYS] AS (expr)
[VIRTUAL | STORED] [NOT NULL | NULL]
[VISIBLE | INVISIBLE]
[UNIQUE [KEY]] [[PRIMARY] KEY]
[COMMENT 'string']
[reference_definition]
[check_constraint_definition]
}
Supported operations
Convert the data types. For more information about supported data types, see Data type conversion.
Specify the NULL or NOT NULL attribute.
Specify the DEFAULT attribute, which can be a constant or a function.
Specify the VISIBLE or INVISIBLE attribute.
Specify AUTO_INCREMENT.
Specify COMMENT.
Specify COLLATE.
Specify a generated column and specify the VIRTUAL or STORED attribute for the column.
Specify the UNIQUE KEY, PRIMARY KEY, or KEY attribute. For more information, see Create an index or a constraint.
Specify the CHECK constraint. For more information, see Create an index or a constraint.
Notice
You can specify the CHECK constraint only in MySQL-compatible tenants of OceanBase Database V3.2.3 or later.
Specify foreign keys. For more information, see Create an index or a constraint.
Ignored clauses and options
Note
The following clauses and options will be ignored and will not be resolved or converted when they are specified in the synchronized DDL statements.
COLUMN_FORMAT
ENGINE_ATTRIBUTE
SECONDARY_ENGINE_ATTRIBUTE
STORAGE
Limitations
Warning
Due to the limitations of a MySQL-compatible tenant of OceanBase Database, an error may be returned when the synchronized DDL statements are converted and executed in a MySQL-compatible tenant of OceanBase Database in the following scenarios.
MySQL-compatible tenants of OceanBase Database do not support specifying certain functions or expressions in the DEFAULT attribute.
MySQL-compatible tenants of OceanBase Database do not support specifying certain functions or expressions in generated columns.
MySQL-compatible tenants of OceanBase Database do not support specifying the UNIQUE KEY, PRIMARY KEY, or KEY attribute for certain field types.
MySQL-compatible tenants of OceanBase Database do not support certain collations.
