Terms in this set (29)
What are the three basic methods for searching and querying attribute data?
(1) selection, (2) query by attribute, and (3) query by geography
essentially questions posed to the database
-easiest way to search and query spatial data
-highlights those attributes of interest, both on-screen and in the attribute table, for display or analysis.
-selects points, lines, and polygons by "point-and-click" or drag a box around features of interest.
-select using a graphic object, such as a circle to highlight all within the object.
-Advanced:selecting subsets of data from the larger dataset ie: create new selection, select frm currently selected, add to current selection, and remove from current selection.
SQL (Structured Query Language)
-is a commonly used computer language developed to query attribute data within a relational database management system.
-Can get subset of attribute info based of specific criteria using particular language elements.
-extended to GIS more recently.
-exact expression depends on GIS file format ie: ANSI SQL & ArcSDE
SELECT, FROM, WHERE, ORDER BY, HAVING
denotes what attribute table fields you wish to view
denotes the attribute table in which the information resides.
denotes the user-defined criteria for the attribute information that must be met in order for it to be included in the output set
denotes the sequence in which the output set will be displayed
denotes the predicate used to filter output from the ORDER BY clause.
employs the statement equal to, less than, less than or equal to etc.
mathematical functions addition, multiplication etc.
AND, OR, XOR, NOT
select records that satisfies both expressions. intersection.
select records that satisfy either one or both expressions. union.
select records that satisfy one and only one of the expressions
used to negate (unselect) an expression that would otherwise be true. complement.
Query by geography (spatial query)
*ARE WITHIN A DISTANCE OF
*ARE COMPLETELY WITHIN
*HAVE THEIR CENTER IN
*SHARE A LINE SEGMENT
*TOUCH THE BOUNDARY OF
*ARE IDENTICAL TO
*ARE CROSSED BY THE OUTLINE OF
*ARE CONTAINED BY.
This oft-used spatial query technique selects all features in the target layer that share a common locale with the source layer. Allows points, lines, or polygon layers to be used as both the source and target layers
ARE WITHIN DISTANCE OF
This technique requires the user to specify some distance value, which is then used to buffer the source layer. All features that intersect this buffer are highlighted in the target layer. Allows points, lines, or polygon layers to be used for both the source and target layers (Figure 6.9). (Chapter 7 "Geospatial Analysis I: Vector Operations", Section 7.2 "Multiple Layer Analysis")
This spatial query technique returns those features that are entirely within the source layer. Features with coincident boundaries are not selected by this query type. Allows for points, lines, or polygons as the source layer, but only polygons can be used as a target layer (Figure 6.10).
ARE COMPLETELY WITHIN
This query selects those features in the target layer whose entire spatial extent occurs within the geometry of the source layer. Allows for points, lines, or polygons as the target layer, but only polygons can be used as a source layer (Figure 6.11).
HAVE THEIR CENTER IN
This technique selects target features whose center, or centroid, is located within the boundary of the source feature dataset. Allows points, lines, or polygon layers to be used as both the source and target layers (Figure 6.12).
SHARE A LINE SEGMENT
This spatial query selects target features whose boundary geometries share a minimum of two adjacent vertices with the source layer. Allows for line or polygon layers to be used for either of the source and target layers (Figure 6.13).
TOUCH THE BOUNDARY OF
This methodology is similar to the INTERSECT spatial query; however, it selects line and polygon features that share a common boundary with target layer. Allows for line or polygon layers to be used as both the source and target layers (Figure 6.14).
ARE IDENTICAL TO
This spatial query returns features that have the exact same geographic location. Can be used on points, lines, or polygons, but the target layer type must be the same as the source layer type (Figure 6.15).
ARE CROSSED BY THE OUTLINE OF
This selection criteria returns features that share a single vertex but not an entire line segment. Allows for line or polygon layers to be used as both source and target layers (Figure 6.16).
This method is similar to the COMPLETELY CONTAIN spatial query; however, features in the target layer will be selected even if the boundaries overlap. Allows for point, line, or polygon features in the target layer when points are used as a source; when line and polygon target layers with a line source; and when only polygon target layers with a polygon source (Figure 6.17).
ARE CONTAINED BY
This method is similar to the ARE COMPLETELY WITHIN spatial query; however, features in the target layer will be selected even if the boundaries overlap. Allows for point, line, or polygon features in the target layer when polygons are used as a source; when point and line target layers with a line source; and when only point target layers with a point source (Figure 6.18).
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