ESQL supports several operators for complex comparison tasks.
If you want to use ESQL to perform a simple comparison, see ESQL simple comparison operators.
BETWEEN operator .-ASYMMETRIC-. >>-expression--+-----+--BETWEEN--+------------+-----------------> '-NOT-' '-SYMMETRIC--' >--endpoint_1--AND--endpoint_2---------------------------------><
This operator exists in two forms, SYMMETRIC and ASYMMETRIC (which is the default if neither is specified). The SYMMETRIC form is equivalent to:
(source>= boundary1 AND source <= boundary2) OR
(source>= boundary2 AND source <= boundary1)
The ASYMMETRIC form is equivalent to:
source>= boundary1 AND source <= boundary2
The ASYMMETRIC form is simpler but returns only the result that you expect when the first boundary value has a smaller value than the second boundary. It is useful only when the boundary condition expressions are literals.
If the operands are of different types, special rules apply. These rules are described in Implicit casts.
EXISTS operator >>-Operand--(--ListExpression--)-------------------------------><The operator EXISTS returns a Boolean value that indicates whether a SELECT function returned one or more values (TRUE) or none (FALSE).
EXISTS(SELECT * FROM something WHERE predicate)
IN operator .-,---------. V | >>-operand_1--+-----+--IN--(----operand_2-+--)----------------->< '-NOT-'
The result is TRUE if the left operand is not NULL and is equal to one of the right operands. The result is FALSE if the left operand is not NULL, and is not equal to one or more of the right operands, none of which have NULL values. Otherwise the result is UNKNOWN. If the operands are of different types, special rules apply. These rules are described in Implicit casts.
operand_1 must evaluate to a scalar value. operand_2 can be a sequence of expressions that return scalars of types comparable with operand_1 or it can be a single expression that returns a LIST. If the LIST is one that is returned from a SELECT function, there can be only a single column in the SelectClause and each ROW in that column is compared with operand_1 for equality.
SET OutputRoot.XMLNSC.Top.Result1 = 30 NOT IN(34, 42, 45)
SET OutputRoot.XMLNSC.Top.Result2 = var1 IN(var2, var3, var4);
SET OutputRoot.XMLNSC.Top.Result3 = 42 IN(
SELECT A FROM InputRoot.XMLNSC.Top.a[] AS A);
SET OutputRoot.XMLNSC.Top.Result4 = 42 IN(
LIST{34,36,37,38,39,40,41,42,43,44});
SET OutputRoot.XMLNSC.Top.Result5 = var1 IN(
InputRoot.XMLNSC.Top.test[]);
IS operator .-TRUE-------. >>-Operand --IS--+-----+--+-FALSE------+----------------------->< '-NOT-' +-INF--------+ +-+INF-------+ +- -INF------+ +-INFINITY---+ +-+INFINITY--+ +- -INFINITY-+ +-NAN--------+ +-NULL-------+ +-NUM--------+ +-NUMBER-----+ '-UNKNOWN----'
The primary purpose of the IS operator is to test whether a value is NULL. You cannot use the comparison operator (=) to test for a NULL value, because the result of comparing any value with NULL is NULL.
You can also use the IS operand to test for the Boolean values TRUE and FALSE, and to test decimal values for special values. These values are denoted by INF, +INF, -INF, NAN (not a number), and NUM (a valid number) in upper, lower, or mixed case. The alternative forms +INFINITY, -INFINITY, and NUMBER are also accepted.
If applied to non-numeric types, the result is FALSE.
LIKE operator >>-source--+-----+--LIKE--pattern--+--------------------+------>< '-NOT-' '-ESCAPE--EscapeChar-'
The result is TRUE if none of the operands are NULL and the source operand matches the pattern operand. The result is FALSE if none of the operands are NULL and the source operand does not match the pattern operand. Otherwise the result is UNKNOWN.
The pattern is specified by a string in which the percent (%) and underscore (_) characters have a special meaning:
Body.Trade.Company LIKE 'I__'
Body.Trade.Company LIKE 'I%'
To use the percent and underscore characters within the expressions that are to be matched, precede the characters with an ESCAPE character, which defaults to the backslash (\) character.
For example, the following predicate finds a match for IBM_Corp.
Body.Trade.Company LIKE 'IBM\_Corp'
You can specify a different escape character by using the ESCAPE clause. For example, you could also specify the previous example in this way:
Body.Trade.Company LIKE 'IBM$_Corp' ESCAPE '$'
SINGULAR operator >>-Operand--(--ListExpression--)-------------------------------><The operator SINGULAR returns a Boolean value of TRUE if the list has exactly one element, otherwise it returns FALSE.