428
Chapter 20: Accessing and Retrieving Data
Working with dynamic data
A web application page is different from a static web page because it can publish data dynamically.
This can involve querying databases, connecting to LDAP or mail servers, and leveraging COM,
DCOM, CORBA, or Java objects to retrieve, update, insert, and delete data at runtime—as your
users interact with pages in their browsers.
For ColdFusion developers, the term data source can refer to a number of different types of
structured content accessible locally or across a network. You can query web sites, LDAP servers,
POP mail servers, and documents in a variety of formats. Most commonly though, a database
drives your applications, and for this discussion a
data source
means the entry point from
ColdFusion to a database.
In this chapter, you build a query to retrieve data from the CompanyInfo data source. In
Windows, this data source connects to a Microsoft Access database (company.mdb
)
. In UNIX,
this data source connects to a dBASE database. In subsequent chapters in this book, you insert
and update data in this database.
To query a database, you must use:
•
ColdFusion data sources
•
The
cfquery
tag
•
SQL commands
Retrieving data
You can query databases to retrieve data at runtime. The retrieved data, called the
record set
, is
stored on that page as a query object. A
query object
is a special entity that contains the record set
values, plus RecordCount, CurrentRow, and ColumnList query variables. You specify the query
object’s name in the
name
attribute of the
cfquery
tag. The query object is often called simply
the
query
.
The following is a simple
cfquery
tag:
<cfquery name = "GetSals" datasource = "CompanyInfo">
SELECT * FROM Employee
ORDER BY LastName
</cfquery>
Note:
The terms “record set” and “query object” are often used synonymously when discussing
record sets for queries. For more information, see
Chapter 22, “Using Query of Queries,”
on page 451
.
When retrieving data from a database, perform the following tasks:
•
To tell ColdFusion how to connect to a database, use the
cfquery
tag on a page.
•
To specify the data that you want to retrieve from the database, write SQL commands inside
the
cfquery
block.
•
Later on the page, reference the query object and use its data values in any tag that presents
data, such as
cfoutput
,
cfgrid
,
cftable
,
cfgraph
, or
cftree
.
Содержание ColdFusion MX
Страница 1: ...Developing ColdFusion MX Applications...
Страница 22: ...22 Contents...
Страница 38: ......
Страница 52: ...52 Chapter 2 Elements of CFML...
Страница 162: ......
Страница 218: ...218 Chapter 10 Writing and Calling User Defined Functions...
Страница 250: ...250 Chapter 11 Building and Using ColdFusion Components...
Страница 264: ...264 Chapter 12 Building Custom CFXAPI Tags...
Страница 266: ......
Страница 314: ...314 Chapter 14 Handling Errors...
Страница 344: ...344 Chapter 15 Using Persistent Data and Locking...
Страница 349: ...About user security 349...
Страница 357: ...Security scenarios 357...
Страница 370: ...370 Chapter 16 Securing Applications...
Страница 388: ...388 Chapter 17 Developing Globalized Applications...
Страница 408: ...408 Chapter 18 Debugging and Troubleshooting Applications...
Страница 410: ......
Страница 426: ...426 Chapter 19 Introduction to Databases and SQL...
Страница 476: ...476 Chapter 22 Using Query of Queries...
Страница 534: ...534 Chapter 24 Building a Search Interface...
Страница 556: ...556 Chapter 25 Using Verity Search Expressions...
Страница 558: ......
Страница 582: ...582 Chapter 26 Retrieving and Formatting Data...
Страница 668: ......
Страница 734: ...734 Chapter 32 Using Web Services...
Страница 760: ...760 Chapter 33 Integrating J2EE and Java Elements in CFML Applications...
Страница 786: ...786 Chapter 34 Integrating COM and CORBA Objects in CFML Applications...
Страница 788: ......
Страница 806: ...806 Chapter 35 Sending and Receiving E Mail...