COLUMNS 
Using the
system table
COLUMNS, you can determine the following database information:
- Columns of table RESERVATION in the sequence in which they were defined, together with the relevant comments
SELECT columnname, comment
FROM DOMAIN.COLUMNS
WHERE tablename = 'RESERVATION' ORDER BY pos
Data types of all columns of table CUSTOMER
SELECT columnname, datatype, len, dec, codetype
FROM DOMAIN.COLUMNS
WHERE tablename = 'CUSTOMER'
All columns of your own Basis tables that have the data type DATE
SELECT tablename,columnname
FROM DOMAIN.COLUMNS
WHERE owner = user
AND tabletype = 'TABLE'
AND datatype = 'DATE'
All columns of your own table HOTEL for which a default value was defined, plus this default value
SELECT columnname, default
FROM DOMAIN.COLUMNS
WHERE owner = user
AND tablename = 'HOTEL'
AND default IS NOT NULL
All primary table columns of table ROOM, sorted according to their sequence in the primary key
SELECT columnname
FROM DOMAIN.COLUMNS
WHERE mode = 'KEY' ORDER BY keypos
All columns defined with NOT NULL of table CUSTOMER
SELECT columnname
FROM DOMAIN.COLUMNS
WHERE tablename = 'CUSTOMER' AND mode = 'MAN'
All columns of table RESERVATION that can be changed by the current user
SELECT columnname
FROM DOMAIN.COLUMNS
WHERE columnprivileges LIKE '*UPD*'
All columns of table RESERVATION that can be changed by the current user and for which the user can pass on this privilege
SELECT columnname
FROM DOMAIN.COLUMNS
WHERE columnprivileges LIKE '*UPD+*'
All table columns that were specified as MYDOMAIN during definition of the domain
SELECT owner, tablename, columnname
FROM DOMAIN.COLUMNS
WHERE domainname = 'MYDOMAIN'

Columns in the index: see
INDEXCOLUMNS
Columns in the referential constraint: see
FOREIGNKEYCOLUMNS
Primary table or view table columns in the view table: see
VIEWCOLUMNS