Can someone point me to any documentation on supported datatypes?

I was creating table using "double" and it failed. Decimal, float,
real all work fine.

I came across the MS SQL to Firebird conversion page and it did
indicate datatype 'double' was supported.

SQL>create table Staff1 (id integer, salary double);

Statement failed, SQLCODE = -104

Dynamic SQL Error
-SQL error code = -104
-Token unknown - line 1, char 136
-,

To my understanding of other database, there precision different
between float and double, that is why I am interested in double.

I guess I could use 'decimal (18, 4).

Any idea?

jml