Expression Builder overview

The Expression Builder is a standard dialog box that is displayed wherever a user-defined expression can be entered. An expression is a statement that combines elements such as data fields, operators, functions, filters, and variables that ACL evaluates and returns a value for.

Depending on the context where the Expression Builder is displayed, ACL checks that the expression evaluates to the required type of value. For example, if you are creating an expression used to filter the records in a view, the expression must evaluate to a logical value of True or False. The filter is applied by displaying only those records that evaluate to True when tested against the logical statement used in the expression.

Figure 1. Expression Builder

The Expression Builder includes the following user interface elements:

  1. Expression text box – Use this text box to create a new expression or edit an existing expression. You can type the required syntax for the expression, and use the lists and buttons in the dialog box to enter required information. When you use the controls on the dialog box, the information is added at the current cursor position in the Expression text box.

  2. Verify button – Click this button to verify the syntax of the statement in the Expression text box. Clicking Verify saves time by allowing you to check the validity of an expression without leaving the Expression Builder.

  3. Save As text box – If you want to permanently save the expression you are creating or editing, you can enter a name for the expression and it is saved with this name when you click OK.

  4. Available Fields list – Lists all of the data fields and computed fields in the selected table. Double-click a field entry to add it to the Expression text box.

  5. From Table drop-down list – If the table is related to one or more other tables, you can select any of the related tables from this drop-down list. An expression can contain fields from one or more related tables, even if the fields do not appear in the current view. You can also build filters that include fields from related tables and see the results in the current view, whether or not you add the fields from the related tables to the view.

  6. Operator buttons, and Date & Time Selector – Click the buttons in this area to add operators, or dates, datetimes, or times, to the Expression text box.

  7. Filters list – Lists the named filters associated with the selected table. Double-click a filter entry to add it to the Expression text box.

  8. Variables list – Lists the variables associated with the selected table. Double-click a variable entry to add it to the Expression text box.

  9. Functions drop-down list – Lists function categories that can be used to filter the functions displayed in the Functions list.

  10. Functions list – Lists the functions available in ACL and their required syntax. Optional parameters are enclosed in angle brackets (< >). Double-click a function to add it to the Expression text box. Depending on the type of function, the parameters can be constants, literals, field names, or expressions, which may include other functions.

    For information about how to use the individual functions in the Functions list, see the ACL Language Reference.

  11. Paste Parameters checkbox – If this checkbox is selected, the function is copied to the Expression text box with named placeholders for each parameter. If the checkbox is not selected, only the function name, including opening and closing parentheses, is copied to the Expression text box.

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