alter

The alter statement is used to add, delete or rename columns to an existing table.

Related function: addColumn, dropColumns!, rename!.

Syntax

alter table tableObj add columnName columnType;
alter table tableObj drop [column] columnName;
alter table tableObj rename [column] columnName to newColumnName;

tableObj can be an in-memory table, a stream table, a DFS table, or a dimension table.

colNames is a string scalar indicating the name of the column to be added.

newColNames is a string scalar indicating the name of the column to be modified.

colTypes is a scalar indicating the data type of the column.

Examples

$ if(existsDatabase("dfs://test")) dropDatabase("dfs://test")
$ create database "dfs://test" partitioned by VALUE(1..10), HASH([SYMBOL, 40]), engine='OLAP', atomic='TRANS', chunkGranularity='TABLE'

$ create table "dfs://test"."pt"(
    id INT,
    deviceId SYMBOL,
    date DATE[comment="time_col", compress="delta"],
    value DOUBLE,
    isFin BOOL
)
partitioned by ID, deviceID

$ pt = loadTable("dfs://test", `pt)
$ alter table pt add location SYMBOL;
$ pt = loadTable("dfs://test", `pt)
$ pt.schema().colDefs

name	typeString	typeInt	comment
id	INT	4
deviceId	SYMBOL	17
date	DATE	6	time_col
value	DOUBLE	16
isFin	BOOL	1
location	SYMBOL	17

$ alter table pt rename location to loc
$ pt = loadTable("dfs://test", `pt)
$ pt.schema().colDefs

name	typeString	typeInt	comment
id	INT	4
deviceId	SYMBOL	17
date	DATE	6	time_col
value	DOUBLE	16
isFin	BOOL	1
loc	SYMBOL	17

$ alter table pt drop value
$ pt = loadTable("dfs://test", `pt)
$ pt.schema().colDefs

name	typeString	typeInt	comment
id	INT	4
deviceId	SYMBOL	17
date	DATE	6	time_col
isFin	BOOL	1
loc	SYMBOL	17