The SQL ALTER TABLE command

The ALTER TABLEcommand is used to add, delete, or modify columns in an existing table.
.The ALTER TABLE command is also used to add and drop various constraints on an existing table.

ALTER OBJECTNAME TABLENAME ADD COLOUMNNAME DATATYPE

The column parameters specify the names of the columns of the table.

The datatype parameter specifies the type of data the column can hold (e.g. varchar, integer, date, etc.).