| People prefer to keep complex data sets in | | | | modulus and unary operators. These operators are |
| databases rather than in flat files because data can | | | | used to build formulae and other mathematical |
| be found and grouped more precisely when it is | | | | expressions. If you are calculating the total value of a |
| stored in a database. The ability to draw data out of | | | | particular group of records, or creating an invoice, |
| a database depends upon the ability to structure | | | | you would use these operators. |
| queries, or requests that define specific records. | | | | The "like" operator can be used to identify less |
| Structuring queries in Access 2007 is relatively easy | | | | specific search criteria. The like operator is used with |
| because Access is designed to handle many different | | | | a wildcard such as ? or *. The ? wildcard substitutes |
| types of operators. | | | | a single character. The *wildcard identifies a string of |
| An operator is a special symbol or reserved word | | | | characters. Using the query "like a?c", Access would |
| that triggers the database to act in a certain way. | | | | produce records that contained aac, abc, acc, adc |
| Access 2007 recognizes several types of operators, | | | | and so on in the search field. Using the query "like |
| including comparison operators, arithmetic operators, | | | | a*c", Access would produce records that contained |
| logical operators and special expressions such as like, | | | | acidic, amoebic, anaerobic, auric or any other field |
| between..and, in, and is null. You may also use | | | | value of any length that started with "a" and ended |
| combinations of these types of operators when | | | | with "c" and was contained within the search field. |
| structuring queries in Access 2007. | | | | Access also recognises "between...and" for identifying |
| Comparison operators ask Access 2007 to perform a | | | | a range of values. In can be used to limit a range of |
| comparison between two values. In a query, a | | | | values, and is null can be used to search for blank or |
| comparison operator can locate all records where a | | | | empty fields. |
| field value is greater than, less than, equal to, not | | | | Access 2007 understands logical operators such as |
| equal to, greater than or equal to, or less than or | | | | and, or, not, xor, eqv and imp. The and operation |
| equal to a specified value. Comparison operators can | | | | returns a true value only when both conditions are |
| be applied to all fields that contain a literal value. A | | | | true. Or returns a true value when either expression |
| literal value is a value that has been directly entered | | | | is true. Not negates the expression. Xor is an |
| into the field. Access recognizes four literals: text, | | | | exclusive or. It returns a true value when either |
| numbers, dates and times, and constants. | | | | expression - but not both - are true or false. Eqv |
| Arithmetic operators are basic mathematical | | | | returns a true value when both expressions are equal |
| operations. Access recognizes addition, subtraction, | | | | and Imp returns a false value if the first expression is |
| multiplication, real and integer division, exponentiation, | | | | true and the second expression is false. |