HP 3000 Manuals

ALLBASE/SQL Reference Manual

Search Condition 

A search condition is a single predicate or several predicates connected
by the logical operators AND or OR. A predicate is a comparison of
expressions that evaluates to a value of TRUE, FALSE, or unknown.  If a
predicate evaluates to TRUE for a row, the row qualifies for the select,
update, or delete operation.  If the predicate evaluates to FALSE or
unknown for a row, the row is not operated on.

Scope 

SQL Data Manipulation Statements

SQL Syntax 

      {BetweenPredicate   } [            {BetweenPredicate   }]
      {ComparisonPredicate} [            {ComparisonPredicate}]
      {ExistsPredicate    } [            {ExistsPredicate    }]
[NOT] {InPredicate        } [{AND} [NOT] {InPredicate        }] [...]
      {LikePredicate      } [{OR }       {LikePredicate      }]
      {NullPredicate      } [            {NullPredicate      }]
      {QuantifiedPredicate} [            {QuantifiedPredicate}]
      {(SearchCondition)  } [            {(SearchCondition)  }]
Parameters 

NOT, AND, OR            are logical operators with the following
                        functions:

                        NOT      reverses the value of the predicate that
                                 follows it.

                        AND      evaluates predicates it joins to TRUE if
                                 they are both TRUE.

                        OR       evaluates predicates it joins to TRUE if
                                 either or both are TRUE.

BetweenPredicate        determines whether an expression is within a
                        certain range of values.

ComparisonPredicate     compares two expressions.

ExistsPredicate         determines whether a subquery returns any
                        non-null values.

InPredicate             determines whether an expression matches an
                        element within a specified set.

LikePredicate           determines whether an expression contains a
                        particular character string pattern.

NullPredicate           determines whether a value is null.

QuantifiedPredicate     determines whether an expression bears a
                        particular relationship to a specified set.

(SearchCondition)       is one of the above predicates, enclosed in
                        parentheses.

Description 

   *   Predicates in a search condition are evaluated as follows:

          *   Predicates in parentheses are evaluated first.

          *   NOT is applied to each predicate.

          *   AND is applied next, left to right.

          *   OR is applied last, left to right.

   *   When a predicate contains an expression that is null, the value of
       the predicate is unknown.  Logical operations on such a predicate
       result in the following values, where a question mark (?)
       represents the unknown value:


          Figure 9-1.  Logical Operations on Predicates Containing NULL Values 

       When the search condition for a row evaluates to unknown, the row
       does not satisfy the search condition and the row is not operated
       on.  Check constraints are an exception; see the section on CREATE
       TABLE or CREATE VIEW.

   *   You can compare only compatible data types.  INTEGER, SMALLINT,
       DECIMAL, FLOAT, and REAL are compatible.  CHAR and VARCHAR are
       compatible, regardless of length.  You can compare items of type
       DATE, TIME, DATETIME, and INTERVAL to literals of type CHAR or
       VARCHAR. ALLBASE/SQL converts the literal before the comparison.
       BINARY and VARBINARY are compatible, regardless of length.

   *   You cannot include a LONG BINARY or LONG VARBINARY data type in a
       predicate except within a long column function.

   *   A SubQuery expression cannot appear on the left-hand side of a
       predicate.

   *   Refer to the "Data Types" and "Expressions" chapters for
       information concerning value extensions and type conversion during
       comparison operations.

MPE/iX 5.5 Documentation