The full standard syntax is below.

<alter column definition> ::=
    ALTER [ COLUMN ] <column name> <alter column action>

<alter column action> ::=
    <set column default clause>
    | <drop column default clause>
    | <add column scope clause>
    | <drop column scope clause>
    | <alter column data type clause>
    | <alter identity column specification>

<alter identity column specification> ::=
    <alter identity column option>...

<alter identity column option> ::=
    <alter sequence generator restart option>
    | SET <basic sequence generator option>

<alter sequence generator restart option> ::=
    RESTART [ WITH <sequence generator restart value> ]

<basic sequence generator option> ::=
    <sequence generator increment by option>
    | <sequence generator maxvalue option>
    | <sequence generator minvalue option>
    | <sequence generator cycle option>