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

**Table 1** ADD COLUMNS parameters
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.