Boolean at a GlanceSubmitted by admin on Fri, 10/03/2008 - 01:02 |
Boolean logic is used to construct search statements by use of a special syntax. The syntax is composed of operators (terms which have unique meanings), which are combined to form expressions (or queries). Boolean is a powerful tool: When you submit a query using Boolean syntax, you are speaking to the search engine in a language it can clearly understand.
Here’s a list of operators and syntax available for constructing Boolean expressions. If a search engine supports Boolean (and many do), it is likely to support all the items in the first table, below.
The Basics (most common)
| operator | meaning |
| AND | BOTH words MUST appear in the document. This term imposes no restrictions on word order or word proximity. |
| AND NOT | EXCLUDES documents containing ANY of the words FOLLOWING the connector. This term imposes no restrictions on word order or word proximity. |
| OR | EITHER word MUST appear in the document. This term imposes no restrictions on word order or word proximity. |
| " " | Creates a PHRASE wherein the combined words or terms MUST appear EXACTLY as written in the document. |
| * | WILDCARD character used to replace ONE OR MORE characters in a word. You cannot use it for the first letter of a word. |
More Advanced Terms (less common)
| operator | meaning |
| NEAR | Similar to AND, only both terms have to be within a specified WORD DISTANCE from one another in order to be scored as a result. |
| AFTER | Similar to NEAR, only the first (left-hand) term before this operator has to occur within a specified word distance AFTER the term on the right side of this operator in order for the source document to be scored as a result. |
| BEFORE | Similar to NEAR, only the first (left-hand) term before this operator has to occur within a specified word distance BEFORE the term on the right side of this operator in order for the source document to be scored as a result. |
| ( ) | Just like in Mathematics, Nested Operators can be used to CHANGE THE PRIORITY in which the connectors operate. |