MACROMEDIA COLDFUSION MX 61-DEVELOPING COLDFUSION MX, Develop Manual

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452 Chapter 22: Using Query of Queries
About record sets
Query of Queries is based on manipulating the record set, which you can create using the
cfquery
tag and other ways.
When you execute a database query, ColdFusion retrieves the data in a record set . In addition to
presenting record set data to the user, you can manipulate this record set to improve your
application’s performance.
Because a record set contains rows (records) and columns (fields), you can think of it as a virtual
database table, or as a spreadsheet. For example, the
cfpop
tag retrieves a record set in which each
row is a message and each column is a message component, such as To, From, and Subject.
Referencing queries as objects
You can reference ColdFusion queries as objects by assigning a query to a variable, as follows:
<cfquery name = "query01"
datasource = "myDNS"
SELECT * FROM CUSTOMERS
</cfquery>
...
<cfset query02 = query01>
The query is not copied; both names point to the same record set data. Therefore, if you make
changes to the table referenced in query01, the original query and the query object called query02
both reflect these changes. If you perform a copy with an array, the array is copied.
Creating a record set
You can perform a Query of Queries on any ColdFusion tag or function that generates a record
set, including the following:
•
cfcollection
•
cfdirectory
•
cfftp
•
cfhttp
•
cfindex
•
cfldap
•
cfmail
•
cfpop
•
cfprocresult
•
cfquery
(against a database or against another Query of Queries)
•
cfsearch
•
cfstoredproc
•
cfwddx
•
the
QueryNew ( );
query function