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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

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.

Parent topic: DDL