User`s guide

There are hundreds of Database Management Systems (DBMS) available for personal computers, and
thousands of applications that access DBMS data. Normally, a company that designs an application
that accesses data, such as Crystal Reports, must develop a means for the application to communicate
with each type of data that a customer might want to use. Crystal Reports does this with the databases
that it can access directly.
On the other hand, if a DBMS simply provides a means by which ODBC can access its data, the DBMS
data becomes an ODBC data source. Any application that can communicate with ODBC (such as
Crystal Reports), will instantly have access to any ODBC data source. With ODBC drivers available for
most common DBMS products, the range of data types that Crystal Reports can use is almost unlimited.
A.3.1 Advantages
Perhaps the biggest advantage to accessing data through ODBC is the ability to access a wide range
of data with just one interface. Since most popular Database Management Systems now offer ODBC
drivers, with more appearing every day, Crystal Reports can use any type of data you have.
Because of the extreme flexibility built into ODBC, you can use the same report file with different ODBC
data sources. For example, you might design a report using an Oracle data source, and later, if your
company switches to Microsoft SQL Server, you can simply change the ODBC data source used by
your report. The only requirement is that the new data source must have the same structure (tables
and fields) that the original data source had (although table names can be different). For more information,
search for the topic called "Changing the data source accessed by a report" in the Crystal Reports
Online Help .
Experienced SQL (Structured Query Language) programmers also benefit from the ODBC standard.
Since Crystal Reports uses SQL to communicate with ODBC, SQL programmers and Database
Administrators can view and edit the SQL statements sent to ODBC, controlling exactly how data is
retrieved from the data source.
Finally, by using SQL pass-through technology to send an SQL statement to ODBC and retrieve an
initial set of data, Crystal Reports off-loads much of the data retrieval and sorting work on to the server
system, freeing up local memory and resources for more important tasks. In addition, only the data
specified by the SQL statement is returned to Crystal Reports, reducing network traffic and the use of
network resources. By working more efficiently with the original data, Crystal Reports saves you time
and effort, and lets you concentrate on the design process and other more important work.
A.3.2 Disadvantages
There are many layers involved in passing data through ODBC from a database to an application. First,
Crystal Reports must request some data. The request must be translated by the ODBC translation layer
into a format that ODBC understands (an SQL statement). ODBC must determine where the requested
data exists, and pass the request on to the ODBC data source. For more information, see DBMS
2012-03-14656
Accessing Data Sources