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
Summary of Contents for ColdFusion MX
Page 1: ...Developing ColdFusion MX Applications...
Page 22: ...22 Contents...
Page 38: ......
Page 52: ...52 Chapter 2 Elements of CFML...
Page 162: ......
Page 218: ...218 Chapter 10 Writing and Calling User Defined Functions...
Page 250: ...250 Chapter 11 Building and Using ColdFusion Components...
Page 264: ...264 Chapter 12 Building Custom CFXAPI Tags...
Page 266: ......
Page 314: ...314 Chapter 14 Handling Errors...
Page 344: ...344 Chapter 15 Using Persistent Data and Locking...
Page 349: ...About user security 349...
Page 357: ...Security scenarios 357...
Page 370: ...370 Chapter 16 Securing Applications...
Page 388: ...388 Chapter 17 Developing Globalized Applications...
Page 408: ...408 Chapter 18 Debugging and Troubleshooting Applications...
Page 410: ......
Page 426: ...426 Chapter 19 Introduction to Databases and SQL...
Page 476: ...476 Chapter 22 Using Query of Queries...
Page 534: ...534 Chapter 24 Building a Search Interface...
Page 556: ...556 Chapter 25 Using Verity Search Expressions...
Page 558: ......
Page 582: ...582 Chapter 26 Retrieving and Formatting Data...
Page 668: ......
Page 734: ...734 Chapter 32 Using Web Services...
Page 760: ...760 Chapter 33 Integrating J2EE and Java Elements in CFML Applications...
Page 786: ...786 Chapter 34 Integrating COM and CORBA Objects in CFML Applications...
Page 788: ......