Database Reference
In-Depth Information
Figure 7-3.
BNF Notations
7.3.1 Select Statement
Based on the Ullman notation, the
SELECT
statement is of the form
Note:
1.
Theta
represents a valid Boolean operator i.e. any of the
following: =, >, <, <>, <=, >=
2.
A
relational expression
is either a relation or an expression
that results in the creation of a relation.
3.
A
condition
is an expression that evaluates to true or false.
Complex conditions may be built by using brackets and
connectors AND, OR, NOT as in normal Boolean logic.
Example 1:
To select all students enrolled in program B.Sc. in MIS, the following
statement (based on the Ullman notation) would apply:
