Slide 8.4: Database terminologies (cont.)

Database Terminologies (Cont.)

Databases, Tables, Rows, and Columns

Different terminologies exist:
- tables or relations,
- rows, tuples, or records, and
- columns, attributes, or fields.

A database is defined to be a set of named tables or relations:
```
   CAP = { customer, agent, product, order }
```

The heading of a table (relational schema) is the set of column names:

 Head( customer ) =
   { cid, cname, city, discnt }
 Head( customer ) =
   cid   cname   city   discnt

A database schema is the set of all relational schemes for a database.

Domains and Datatypes

1SQL> CREATE TABLE customer3 (
2  2    cid    CHAR(5),
3  3    cname  VARCHAR(32),
4  4    city   VARCHAR(32),
5  5    discnt REAL );

A domain is the set where an attribute of a table takes on values from:
- The domain of the attribute city might be the set of all character strings corresponding to cities in the US.
- The domain of the discnt column might be defined as consisting of all floating-point numbers between 0.00 and 20.00.