Name
and — Returns false if a value of some argument is false, otherwise returns true.
Synopsis
boolean
and
(
|
val1 boolean , |
| val2 boolean , | |
| ... , | |
valN
boolean
); |
Description
This function calculates the values of its arguments from left to right. If the value of the calculated parameter is false, the function returns false immediately, without calculating the remaining parameters. If the list of arguments ends without any false value calculated, the function returns true (thus it will return true if called without arguments).
The name of this function is the same as the name of "and" XPATH and XQUERY operator. Thus it must be surrounded by double quotes when used in XPATH or XQUERY expressions. Moreover, this function is not a part of XPATH standard, so it cannot be used if portability is important.
Parameters
vali
Value of boolean expression argument
Return Types
boolean
Examples
Example 24.562. Control over sequence of search operations
If two conditions must be checked, where one is simple and another is hard to calculate, then "and" may be used to calculate second condition only if first is true, to reduce average time of processing
"and" ( authors,
document(concat('http://www.lib20.org/findxml.cgi?isbn=',@isbn))/status[@outofprint='NO'] )