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Off-Loading Record Selection to the Database Server

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The most important thing you can do to speed up report processing is to limit the amount of data that is returned from the database. Your primary tool for doing this is the record selection formula.

Crystal Reports analyzes your record selection formula and generates an SQL query from it. This SQL query is then processed by the database, which sends the resulting records back to Crystal Reports. Crystal Reports then evaluates the record selection formula locally for each of the records retrieved from the database, thereby calculating the set of records used to generate the report.

Unnecessary records are eliminated at two stages: at the database with the SQL query and within Crystal Reports by the record selection formula. For speed, you want as many records as possible to be eliminated in the first stage. By designing your record selection formula effectively, you can off-load much of the processing to the database server, thus eliminating unnecessary records before returning them to Crystal Reports. This is commonly called Pushing Down Record Selection to the Database Server.

Parameter Fields

Instead of displaying all of a report's data every time the report is opened, you can create parameter fields that prompt users to specify the data they want to see. To decrease the amount of data transferred from the database server, incorporate these parameter fields right into your record selection formula.

In general, parameter fields provide interactivity for users, who respond to the parameter prompts in order to specify the data they want to see. However, by incorporating your parameter fields right into your record selection formula, you not only provide interactivity, but you also decrease data transfer and increase performance.

You can add a parameter field to your record selection formula by using the Select Expert or the Record Selection Formula Editor. When using the Record Selection Formula Editor, you treat the parameter field as you would any other field. See Incorporating Parameters into Formulas.

SQL Expression Fields

To maintain optimum report processing speeds, avoid using formulas (whether Crystal or Basic syntax) within record selection formulas. Instead, replace the original formula with an equivalent SQL Expression field, and then incorporate the SQL Expression field into your record selection formula. Doing so will greatly improve the chances of your record selection being pushed down to the server.

In addition, you should avoid sorting, grouping, or totaling on a formula field (whether Crystal or Basic syntax). Instead, replace the original formula field with an equivalent SQL Expression field, and then sort, group, or total on the SQL Expression Field. Again, this will greatly improve the chances of the processing being done on the server.

Finally, if your database supports Case Logic, and your report needs to summarize an If-Then-Else formula calculation, replace the formula with an SQL Expression field. In such cases, SQL Expression fields enable Crystal Reports to perform the report's grouping on the server. See SQL Expressions.

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