Report Studio

An expression is any combination of operators, constants, functions, and other components that evaluates to a single value. You build expressions to create calculation and filter definitions. A calculation is an expression that you use to create a new value from existing values contained within a data item. A filter is an expression that you use to retrieve a specific subset of records.

The expression editor shows the expression components that are supported by the data source in which the metadata is stored. For example, if you import metadata from an Oracle data source, the expression editor shows only the elements that are supported in Oracle.

When creating an expression that will be used in a double-byte environment, such as Japanese, the only special characters that will work are ASCII-7 and ~ -- || - $ ¢ £ ¬.

Not all data sources support functions the same way. The data modeler can set a quality of service indicator on functions to give a visual clue about the behavior of the functions. Report authors can use the quality of service indicators to determine which functions to use in a report. The quality of service indicators are:

• not available (X)
  This function is not available for any data sources in the package
• limited availability (!!)
  The function is not available for some data sources in the package
• poor performance (!)
  The function is available for all data sources in the package but may have poor performance in some data sources
• unconstrained (no symbol)
  The function is available for all data sources

Related Topics:

• Concatenating Strings—How to concatenate strings in expression editor.
• Common Functions—Some common functions for use in Expression Editor.
• Constructs—About the constructs available in Expression Editor.
• Operators—About the operators available in Expression Editor.

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