ADD COLUMNS¶
Function¶
This command is used to add a column to an existing table.
Syntax¶
ALTER TABLE [db_name.]table_name ADD COLUMNS (col_name data_type,...) TBLPROPERTIES(''COLUMNPROPERTIES.columnName.shared_column'='sharedFolder.sharedColumnName,...', 'DEFAULT.VALUE.COLUMN_NAME'='default_value');
Parameter Description¶
Parameter | Description |
|---|---|
db_name | Database name. If this parameter is not specified, the current database is selected. |
table_name | Table name. |
col_name data_type | Name of a comma-separated column with a data type. It consists of letters, digits, and underscores (_). Note When creating a CarbonData table, do not name columns as tupleId, PositionId, and PositionReference because they will be used in UPDATE, DELETE, and secondary index commands. |
Precautions¶
Only shared_column and default_value are read. If any other property name is specified, no error will be thrown and the property will be ignored.
If no default value is specified, the default value of the new column is considered null.
If filter is applied to the column, new columns will not be added during sort. New columns may affect query performance.
Examples¶
ALTER TABLE carbon ADD COLUMNS (a1 INT, b1 STRING);
ALTER TABLE carbon ADD COLUMNS (a1 INT, b1 STRING) TBLPROPERTIES('COLUMNPROPERTIES.b1.shared_column'='sharedFolder.b1');
ALTER TABLE carbon ADD COLUMNS (a1 INT, b1 STRING) TBLPROPERTIES('DEFAULT.VALUE.a1'='10');
System Response¶
The newly added column can be displayed by running the DESCRIBE command.