This topic describes the supported conversion scope of ALTER TABLE DDL operations for modifying, dropping, and adding column attributes during data migration from an Oracle database to an Oracle-compatible tenant of OceanBase Database.
Syntax
column_clauses:
{ { add_column_clause
| modify_column_clauses
| drop_column_clause
| add_period_clause
| drop_period_clause
}...
| rename_column_clause
| { modify_collection_retrieval }...
| { modify_LOB_storage_clause }...
| { alter_varray_col_properties }...
}
add_column_clause:
ADD
( {column_definition | virtual_column_definition
[, column_definition | virtual_column_definition] ...
} )
[ column_properties ]
[ ( out_of_line_part_storage [, out_of_line_part_storage]... ) ]
modify_column_clauses:
MODIFY
{ ( modify_col_properties | modify_virtcol_properties
[, modify_col_properties | modify_virtcol_properties ]... )
| ( modify_col_visibility [, modify_col_visibility ]... )
| modify_col_substitutable
}
drop_column_clause:
{ SET UNUSED { COLUMN column
| (column [, column ]...)
}
[ { CASCADE CONSTRAINTS | INVALIDATE }... ]
[ ONLINE ]
| DROP { COLUMN column
| (column [, column ]...)
}
[ { CASCADE CONSTRAINTS | INVALIDATE }... ]
[ CHECKPOINT integer ]
| DROP { UNUSED COLUMNS
| COLUMNS CONTINUE
}
[ CHECKPOINT integer ]
}
add_period_clause:
ADD ( period_definition )
drop_period_clause:
DROP ( PERIOD FOR valid_time_column )
rename_column_clause:
RENAME COLUMN old_name TO new_name
modify_collection_retrieval:
MODIFY NESTED TABLE collection_item
RETURN AS { LOCATOR | VALUE }
modify_LOB_storage_clause:
MODIFY LOB (LOB_item)
(modify_LOB_parameters)
alter_varray_col_properties:
MODIFY VARRAY varray_item
( modify_LOB_parameters )
Supported operations
Renaming columns by using the
rename_column_clauseclause is supported. For more information, see Modify, drop, and add column attributes.Adding columns and constraint attributes by using the
add_column_clausesclause is supported. For more information, see Add columns and column attributes.Modifying column attributes by using the
modify_column_clausesclause is supported. For more information, see Modify column attributes.Dropping columns by using the
drop_column_clauseclause is supported. For more information, see Drop columns.
Unsupported operations
Modifying the result set retrieved from the database by using the
modify_collection_retrievalclause is not supported. An error will be returned when you perform this operation.Modifying the physical attribute of the LOB_item by using the
modify_LOB_storage_clauseclause is not supported. An error will be returned when you perform this operation.Modifying the LOB storage characteristics of the VARRAY type by using the
alter_varray_col_propertiesclause is not supported. An error will be returned when you perform this operation.