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An expression is the part of a query that specifies the conditions. For example, an expression might specify all parcels on a particular street whose area is larger than 4000 square feet. Only parcels that meet those criteria are displayed or selected by a query containing this expression.
A complete query also specifies the set of data to which the conditions are applied and the action to apply to the data that meets the conditions. For example, you can query a particular feature layer in a map and either display or hide data in that layer, depending on whether it meets the query conditions or not.
In practice, you specify the data set by selecting the feature class or layer to query before you build the expression. You specify the action to apply when you select the command or option for building the expression. For example, in AutoCAD Map 3D, you might select Query to Add To Map or Search To Select.
The title bar for the dialog box in which you create expressions will be different, depending on the command you choose. The contents of the dialog box are much the same, no matter what it is called. In AutoCAD Map 3D, you can create expressions for geospatial features from the following locations:
| Command | Title Bar Contents |
|---|---|
Edit menu  Search |
Search For Features Across Multiple Layers |
| Right-click a Display Manager layer Query
To Filter Data |
Create Query |
| Data Table Search To Select |
Search To Select |
| Data Connect Add To Map With Query |
Create Query |
| Data Table Create A Calculation |
Create A Calculation |
| Data Table Set Split And Merge
Rules |
Split Rule Expression/Merge Rule Expression |
| Style Editor Style Label Property
To Display |
Create/Modify Expressions |