Search Condition (search_condition)

A search condition (search_condition) links statements that can be true, false, or undefined. Rows in a table may be found that fulfill several conditions that are linked with AND or OR.

Structure

Syntax Syntax

<search_condition> ::=
  <boolean_term>
| <search_condition> OR <boolean_term>

<boolean_term> ::=
  <boolean_factor>
| <boolean_term> AND <boolean_factor>

<boolean_factor> ::=
  [NOT] <predicate>
| [NOT] (<search_condition>)

End of the code.

In the syntax element boolean_factor, the Boolean values (BOOLEAN) to be linked or their negation (NOT) are determined.

Examples

SQL Tutorial, Conditions: Comparison, AND, OR, BETWEEN, IN, Arithmetic Operations, Negative Conditions: NOT

Explanation

Predicates in a WHERE clause are applied to the specified row or a group of rows in a table formed with the GROUP clause (see: Table Expression (table_expression). The results are linked using the specified Boolean operators (AND, OR, NOT).

If no parentheses are used, the precedence of the operators is as follows: NOT has a higher precedence than AND and OR. AND has a higher precedence than OR. Operators with the same precedence are evaluated from left to right.

NOT

`X`	`NOT(x)`
True	False
False	True
Undefined	Undefined

x AND y

x AND y	False	Undefined	True
False	False	False	False
Undefined	False	Undefined	Undefined
True	False	Undefined	True

x OR y

x OR y	False	Undefined	True
False	False	Undefined	True
Undefined	Undefined	Undefined	True
True	True	True	True

Note Note

A specific form of search condition is required for the SQL Optimizer to be able to determine the most efficient search strategy. For more information, see Concepts of the Database, Search Conditions.

End of the note.