Operator Rule of Precedence Conditional Operators are evaluated first NOT NOT is evaluated first. AND AND is evaluated next. OR, XOR OR and XOR are evaluated last. Note: Operators of equal precedence are evaluated from left to right in the expression.Parentheses can be used to explicitly determine the order of evaluation, overriding the order described…
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Boolean expressions use Boolean operators to compare operands (typically, conditional expressions). When evaluated, Boolean expressions yield a logical result (true or false), depending on the nature of the Boolean operator and the values of the conditional expressions. The standard rules of precedence for Boolean evaluation are used. The software ceases to evaluate a Boolean expression…
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The software automatically determines if it can use indexes when it looks for records in the database. If the software cannot use an available index, each record in the record-containing objects must be scanned (a potentially slower process). In some cases, the software cannot use an available index if the data type of the indexed…
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Certain characters, such as quotation marks and the backslash, have special functions in the software. If you need to use one of these metacharacters as a literal character in a string, you must “escape” the special function by inserting a backslash ( – Escape) preceding the metacharacter as shown in the following example: ‘This is…
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If you need a place a character not normally available from the keyboard into a character literal, use the backslash to create the hex code for that character as shown in the following example: ‘This string has an ASCII escape generated by hex 1B (1B)’ The two characters immediately following a quoted backslash are treated…
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A character literal is any string of characters enclosed in quotation marks as shown in the following example: ‘This is a character string.’ “This is a character string, too.” For convenience, you can enter character literals without the delimiting quotation marks; however, quotation marks are required in some situations. The rules for using quotation marks…
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Conditional expressions use the conditional operators to compare operands (typically, value expressions). When evaluated, conditional expressions yield a logical result (true or false), depending if the condition is satisfied. Conditional Operators Operator Condition Being Evaluated expr = expr The values are equal. expr expr The values are not equal. expr = expr The left-hand value…
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The conditional operators LIKE and = (equals) can be used to construct expressions in which the condition involves matching a value to a pattern rather than to another explicit value. The patterns are usually quoted character strings constructed using special wildcard characters in addition to literal characters. LIKE Patterns Patterns for use with the LIKE…
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When the result of a functional expression is a numeric value, the result contains as many decimal places as are found in the arguments of the function. If the function has several arguments with varying numbers of decimal places, the result takes on the number of decimal places found in the argument with the most…
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A functional expression is a value expression that consists of a function keyword and its associated arguments. Examples of Functional Expressions $absolute(6-11) Result is 5. $length(“Smith”) Result is 5. $cos(0) Result is 1. $log10(2*50) Result is 2. $year(19990923) Result is 1999. $maxof($absolute(-10),4+5) Result is 10.
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