Predicates are expressions which return a Boolean value as a result, that is, FALSE, TRUE, or NULL (or its alias, UNKNOWN).
Predicates can be used as follows:
- In the SELECT list as well as in the WHERE and HAVING clause of a SELECT query
- In the WHERE clause of the UPDATE and DELETE statements
- In the ON clause and the WHERE clauses of the MERGE statement
The supported predicates in Exasol include
In a complex expression, the precedence of the predicate determines the order in which predicates are evaluated. The following table defines this in descending order, that is, the predicates of the first row will be evaluated first. However, you can specify the desired evaluation sequence by enclosing the expressions in parentheses.
| Predicates | Designation |
|---|---|
| =, !=, <, <=, >, >= | Comparison predicates |
| [NOT] BETWEEN, EXISTS, [NOT] IN, IS [NOT] NULL, [NOT] REGEXP_LIKE, [NOT] LIKE, IS [NOT] JSON | Special predicates |
| NOT | Logical negation |
| AND | Conjunction |
| OR | Disjunction |
