A comparison predicate specifies a comparison between two values or lists of values.

expression, expression list, subquery

The following operators are available for comparing two values:
<, >, <>, !=, =, <=, >= ( comp op)

Value lists can only be compared with the = and <> operators ( equal or not).

The subquery must supply a result table (see result table name) that contains the same number of columns as the number of values on the left-hand side of the operator. The result table may contain no more than one row.

The list of values specified to the right of the equal or not operator ( expression list ) must contain the same number of values as specified in the value list in front of the equal or not operator.

The JOIN predicate is a special case.

• The values x and y must be comparable with one another.
• Numbers are compared to one another according to their algebraic values.
• Character strings are compared character by character.
  Any blanks (code attribute ASCII, EBCDIC, see code tables) or binary zeros (code attribute BYTE) at the end of one or both of the character strings are removed.
  If the character strings have different code attributes (ASCII and EBCDIC), one of the two strings is converted implicitly so that they both have the same code attribute.
  Two character strings are identical if they have the same characters in all positions.
  The relationship between two character strings that are not identical is defined by the first character that differs in a comparison from left to right. This comparison is performed in accordance with the code attribute selected for this column (ASCII, EBCDIC, or BYTE).
• If x or y are NULL values (see data type), or if the result of the subquery is empty, (x <comp op> y) is not defined.

If a value list ( expression list ) is specified on the left of the comparison operator equal or not , x is the value list that comprises the results of the values x1, x2, ..., xn in this list. y is the result of the subquery or the result of the second value list. A value list y consists of the results of the values y 1 , y 2 , ..., yn.

• A value xm must be comparable with the associated value ym.
• x=y is true if for xm=ym for all m=1, ..., n.
• x<>y is true if at least xm<>ym for at least one m.
• (x <equal or not> y) is undefined (not known) if there is no m for which (xm <equal or not> ym) is false and if there is at least one m for which (xm <equal or not> ym) is undefined.
• If one xm or one ym is a NULL value, or if the result of the subquery is empty, (x <equal or not> y) is undefined.

TITLE	NAME
Comp	DATASOFT
Comp	TOOLware