Можно. У тебя что, док нету? Там же написано всё. Вот тебе, раз ты доки не читаешь
ALTER TABLE table <operation> [, <operation> …];
<operation> = {ADD <col_def>
| ADD <tconstraint>
| ALTER [COLUMN] column_name <alt_col_clause>
| DROP col
| DROP CONSTRAINT constraint}
<alt_col_clause> = {TO new_col_name
| TYPE new_col_datatype
| POSITION new_col_position}
<col_def> = col {< datatype> | COMPUTED [BY] (< expr>) | domain}
[DEFAULT { literal | NULL | USER}]
[NOT NULL]
[ <col_constraint>]
[COLLATE collation]
< datatype> =
{SMALLINT | INTEGER | FLOAT | DOUBLE PRECISION}[ <array_dim>]
| (DATE | TIME | TIMESTAMP}[ <array_dim>]
| {DECIMAL | NUMERIC} [( precision [, scale])] [ <array_dim>]
| {CHAR | CHARACTER | CHARACTER VARYING | VARCHAR} [( int)]
[ <array_dim>] [CHARACTER SET charname]
| {NCHAR | NATIONAL CHARACTER | NATIONAL CHAR}
[VARYING] [( int)] [ <array_dim>]
| BLOB [SUB_TYPE { int | subtype_name}] [SEGMENT SIZE int]
[CHARACTER SET charname]
| BLOB [( seglen [, subtype])] <array_dim> = [[x:]y [, [x:]y …]]
< expr> = A valid SQL expression that results in a single value.
<col_constraint> = [CONSTRAINT constraint]
{ UNIQUE
| PRIMARY KEY
| REFERENCES other_table [( other_col [, other_col …])]
[ON DELETE {NO ACTION|CASCADE|SET DEFAULT|SET NULL}]
[ON UPDATE {NO ACTION|CASCADE|SET DEFAULT|SET NULL}]
| CHECK ( <search_condition>)}
<tconstraint> = [CONSTRAINT constraint]
{{PRIMARY KEY | UNIQUE} ( col [, col …])
| FOREIGN KEY ( col [, col …]) REFERENCES other_table
[ON DELETE {NO ACTION|CASCADE|SET DEFAULT|SET NULL}]
[ON UPDATE {NO ACTION|CASCADE|SET DEFAULT|SET NULL}]
| CHECK ( <search_condition>)}
CHAPTER 2 SQL STATEMENT AND FUNCTION REFERENCE
<search_condition> = <val> <operator> { <val> | ( <select_one>)}
| <val> [NOT] BETWEEN <val> AND <val>
| <val> [NOT] LIKE <val> [ESCAPE <val>]
| <val> [NOT] IN ( <val> [ , <val> …] | <select_list>)
| <val> IS [NOT] NULL
| <val> {>= | <=}
| <val> [NOT] {= | < | >}
| {ALL | SOME | ANY} ( <select_list>)
| EXISTS ( <select_expr>)
| SINGULAR ( <select_expr>)
| <val> [NOT] CONTAINING <val>
| <val> [NOT] STARTING [WITH] <val>
| ( <search_condition>)
| NOT <search_condition>
| <search_condition> OR <search_condition>
| <search_condition> AND <search_condition>
<val> = { col [ <array_dim>] | : variable
| <constant> | <expr> | <function>
| udf ([ <val> [, <val> …]])
| NULL | USER | RDB$DB_KEY | ? }
[COLLATE collation]
<constant> = num | ' string' | charsetname ' string'
<function> = COUNT (* | [ALL] <val> | DISTINCT <val>)
| SUM ([ALL] <val> | DISTINCT <val>)
| AVG ([ALL] <val> | DISTINCT <val>)
| MAX ([ALL] <val> | DISTINCT <val>)
| MIN ([ALL] <val> | DISTINCT <val>)
| CAST ( <val> AS <datatype>)
| UPPER ( <val>)
| GEN_ID ( generator, <val>)
<operator> = {= | < | > | <= | >= | !< | !> | <> | !=}
<select_one> = SELECT on a single column; returns exactly one value.
<select_list> = SELECT on a single column; returns zero or more values.
<select_expr> = SELECT on a list of values; returns zero or more
values.
