Database Reference
In-Depth Information
Note:
1.
The
Function-Spec-Clause
may involve any combination of
a vast list of SQL functions, some of which will be mentioned
in subsequent sections. The following are some categories of
functions that are applicable:
•
Row functions
•
Date functions
•
Data conversion functions
•
Aggregation (group) functions
•
Programmer defined functions
2.
Condition is as discussed in Chapter 8 (WFFs) except for the
following:
a.
In SQL, the construct IF <Comparison> THEN WFF is
not allowed.
b.
The syntax for using the existential quantifier s
slightly different — the tuple variable is implicit
rather than explicit.
c.
The universal quantifier is not widely supported in
SQL implementations. However, in light of available
substitution rules (review section 8.4) we will not pursue
its use any further.
3.
DISTINCT stipulates that unique tuples will be provided as
output where duplicate may occur.
4.
A scalar expression is an appropriate combination of
columns/literals and arithmetic operators, which results in a
scalar value (typically numeric or alphanumeric). The valid
scalar operators are multiplication (*), division (/), addition (+),
subtraction (-) and concatenation (||).
5.
Relational operators used in the
Where-Clause
or
Having-
Clause
include the following:
We will start by looking as simple examples, then pull in additional features
as we proceed.
