Search Condition; Considerations For Search Condition - HP Neoview SQL Reference Manual

Search Condition

A search condition is used to choose rows from tables or views, depending on the result of
applying the condition to rows. The condition is a Boolean expression consisting of predicates
combined together with OR, AND, and NOT operators.
You can use a search condition in the WHERE clause of a SELECT, DELETE, or UPDATE
statement, the HAVING clause of a SELECT statement, the searched form of a CASE expression,
the ON clause of a SELECT statement that involves a join, a CHECK constraint, or a ROWS
SINCE sequence function.
search-condition is:
boolean-term | search-condition OR boolean-term
boolean-term is:
boolean-factor | boolean-term AND boolean-factor
boolean-factor is:
[NOT] boolean-primary
boolean-primary is:
predicate | (search-condition)
OR
specifies the resulting search condition is true if and only if either of the surrounding
predicates or search conditions is true.
AND
specifies the resulting search condition is true if and only if both the surrounding predicates
or search conditions are true.
NOT
reverses the truth value of its operand—the following predicate or search condition.
predicate
is a BETWEEN, comparison, EXISTS, IN, LIKE, NULL, or quantified comparison predicate.
A predicate specifies conditions that must be satisfied for a row to be chosen. See
(page 286)

Considerations for Search Condition

Order of Evaluation
SQL evaluates search conditions in this order:
1. Predicates within parentheses
2. NOT
3. AND
4. OR
Column References
Within a search condition, a reference to a column refers to the value of that column in the row
currently being evaluated by the search condition.
Subqueries
If a search condition includes a subquery and the subquery returns no values, the predicate
evaluates to null. See
and individual entries.
"Subquery" (page 307).
"Predicates"
Search Condition 305