The first constraint on any column is the one that is implicit in the data type for the column. When you choose a data type, you constrain the column so that it contains only values that can be represented by that data type.
Each data type represents certain kinds of information and not others. The correct data type for a column is the one that represents all the data values that are proper for that column but as few as possible of the values that are not proper for it.
This chapter describes built-in data types.
For information about the extended data types that Dynamic Server supports, see Creating and Using Extended Data Types in Dynamic Server.