Domain Types in SQL

1. SQL standard supports a restricted set of domain types:
   • Fixed length character string, user-specified length.
   • Fixed point number, user-specified precision.

   • Integer, machine dependent precision.
   • Small integer, machine dependent subset of integer type.

   • Floating point, user-specified precision.
   • Floating point and double precision floating point with machine dependent precision.
2. Some SQL implementations include date type. This allows operations on dates, e.g. .

3. Comparisons between compatible domains are usually allowed. To compare an integer and a small integer, the small integer is cast as an integer. This is known as type coercion.