[NOT]		predicate
			(search-condition)
	search-condition			AND		search-condition
				OR

This document covers the following topics:

• Search Condition

• Predicate

---

Search Condition

A search-condition can consist of a simple predicate or multiple search-conditions. Multiple search-conditions are combined with the Boolean operators AND, OR and NOT, and can contain parentheses if required to indicate a desired order of evaluation.

Example

DEFINE DATA LOCAL 
01 NAME   (A20) 
01 AGE    (I2) 
END-DEFINE 
... 
SELECT * 
  INTO NAME, AGE 
  FROM SQL-PERSONNEL 
  WHERE AGE = 32 AND NAME > 'K' 
END-SELECT 
...

Predicate

	scalar-expression comparison		scalar-expression
			subquery
	scalar-expression  [NOT] BETWEEN scalar-expression  AND scalar-expression
	column-reference [NOT] LIKE atom
	column-reference IS [NOT] NULL
	scalar-expression [NOT] IN		subquery
			(atom, )
	scalar-expression comparison		ALL ANY SOME		subquery
	EXISTS subquery
	XMLEXISTS (xquery-expression-constant{BY REF|PASSING xquery-argument,})

A predicate specifies a condition that can be "true", "false" or "unknown".

In a search-condition, a predicate can consist of a simple or complex comparison operation or other kinds of conditions.

Example:

SELECT NAME, AGE 
  INTO VIEW PERS 
  FROM SQL-PERSONNEL 
  WHERE AGE BETWEEN 20 AND 30    
    0R AGE IN ( 32, 34, 36 ) 
    AND NAME LIKE '%er' 
    ...

The individual predicates are explained in the following topics (for further information on predicates, please refer to the relevant literature). According to the syntax above, they are called as follows:

• Comparison Predicate

• BETWEEN Predicate

• LIKE Predicate

• NULL Predicate

• IN Predicate

• Quantified Predicate

• EXISTS Predicate

• XMLEXISTS Predicate

Comparison Predicate

{scalar-expression comparison scalar-expression}

A comparison predicate compares two values or a set of values with another set of values.

In the syntax diagram above, comparison can be one of the following operators:

=	equal to
<	less than
>	greater than
<=	less than or equal to
>=	greater than or equal to
<>	not equal to

See information on scalar-expression.

Subquery

(select-expression)

A subquery is a select-expression that is nested inside another such expression.

Example:

DEFINE DATA LOCAL 
1 #NAME    (A20) 
1 #PERSNR  (I4) 
END-DEFINE 
... 
SELECT NAME, PERSNR 
  INTO #NAME, #PERSNR 
  FROM SQL-PERSONNEL 
  WHERE PERSNR IN 
    ( SELECT PERSNR 
        FROM SQL-AUTOMOBILES 
        WHERE COLOR = 'black' )  
        ... 
END-SELECT

For further information, see Select Expressions.

BETWEEN Predicate

scalar-expression [NOT] BETWEEN scalar-expression AND scalar-expression

A BETWEEN predicate compares a value with a range of values.

See information on scalar-expression.

LIKE Predicate

column-reference [NOT] LIKE atom

A LIKE predicate searches for strings that have a certain pattern.

See information on column-reference and atom.

NULL Predicate

column-reference		IS [NOT] NULL
		ISNULL
		NOTNULL

A NULL predicate tests for null values.

See information on column-reference.

IN Predicate

scalar-expression [NOT] IN		subquery
		(atom)

An IN predicate compares a value or a set of values with a collection of values.

See information on scalar-expression and atom.

See information on subquery.

Quantified Predicate

scalar-expression comparison		ALL		subquery
		ANY
		SOME

A quantified predicate compares a value or a set of values with a collection of values.

See information on scalar-expression, comparison and subquery.

EXISTS Predicate

EXISTS subquery

An EXISTS predicate tests for the existence of certain rows.

The EXISTS predicate evaluates to true only if the result of evaluating the subquery is not empty; that is, if there exists at least one record (row) in the FROM table of the subquery satisfying the search condition of the WHERE clause of this subquery.

Example of EXISTS:

DEFINE DATA LOCAL 
1 #NAME    (A20) 
END-DEFINE 
... 
SELECT NAME 
  INTO #NAME 
  FROM SQL-PERSONNEL 
  WHERE EXISTS 
    ( SELECT * 
      FROM SQL-EMPLOYEES 
      WHERE PERSNR > 1000  
        AND NAME < 'L' ) 
        ... 
END-SELECT 
...

See information on subquery.

XMLEXISTS Predicate

XMLEXISTS (xquery-expression-constant		BY REF		)
		PASSING xquery-argument,...

xquery-argument

	xquery-context-item-expression
	xquery-context-item-expression AS identifier

The XMLEXISTS predicate belongs to the Natural SQL Extended Set.

The XMLEXISTS predicate tests whether an XPATH expression returns a sequence of one or more items. For further information, see the IBM Db2 XML Guide.