The ISNULL function checks for data within a cell - if a cell contains no data it "ISNULL." The basic syntax for using ISNULL in Crystal Report formulas is as follows:

IF ISNULL({Constituent.LastName}) THEN {Constituent.OrgName} ELSE {Constituent.LastName}

The formula will check the LastName field in the Constituent table, and determine if it is blank. If it contains no data, the formula will display the OrgName field. If there is data in the field, however, the LastName will be displayed.

The same results can also be obtained from the following formula:

IF NOT ISNULL({Constituent.LastName}) THEN {Constituent.LastName} ELSE {Constituent.OrgName}

Note: When using the ISNULL syntax as part of a more complex formula, the isnull statement will need to be at the beginning of the formula since the NULL values are evaluated first. EXAMPLE: IF ISNULL({Constituent.LastName}) OR {Constituent.LastName} = "" THEN {Constituent.OrgName}