Under "Structure" tab of a table, set Add 1 column(s) a_column_name, and click the "Go" button. Type in a column name, change Type to SET, insert comma-delimited values (this example uses three), and ...

When trying to execute the following query in H2 database it fails. However, the same query works in mariadb 10.2 ALTER TABLE employee ADD COLUMN IF NOT exists salary INT(11) NOT NULL, ADD COLUMN IF ...