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Data Queries

Data Queries. Selecting features in ArcMap. Data queries. Important part of a GIS project Can be a part of your data preparation or final analysis Data Queries (selecting data based on a question or criteria) Attribute Query Spatial Data Query. Attribute Data Query.

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Data Queries

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  1. Data Queries Selecting features in ArcMap

  2. Data queries • Important part of a GIS project • Can be a part of your data preparation or final analysis • Data Queries (selecting data based on a question or criteria) • Attribute Query • Spatial Data Query

  3. Attribute Data Query • SQL (Structure Query Language) is used select records from an attribute table • Example of a SQL statement for retrieving data Select * Fromcounties WhereNAME = Monterey • Query Expressions • Boolean expressions • Combination of field, a value, and a logical operator (=, +, - , etc..) • Boolean connectors (AND, OR, XOR, NOT) • Connects two expressions

  4. Query Expressions Expression • Combination of field (column), value, and an operator • Example: • Name = Monterey • Pop2000 >=400,000 • State_Name= Calfornia Connectors • Keywords that connect two expressions • State_Name = California AND Pop2000>= 400,000 • State_Name = California OR Pop2000>= 400,000

  5. AND Connector • State_Name = California AND Pop2000 >= 400,000 • AND - satisfy both criteria - intersection

  6. OR Connector • State_Name = California OR Pop2000 >= 400,000 • OR - satisfy either one or both criteria - union

  7. Spatial Data Query 3 Ways to select features spatially (by location) • Feature selection by cursor - (select features tools) • Feature selection by graphic - (draw a graphic and use it to select features) • Feature selection by spatial relationship • Containment (fall within a feature) • Intersect (intersect a feature) • Proximity ( within a specified distance)

  8. Working with selected features • create new selection • add to currently selected features • remove from currently selected features • select from currently selected features You can add, remove or select from currently selected features using location and attribute queries.

  9. Isolating your selected features • Permanently save your selected features • save as new data file (shapefile or geodatabase) • Right-click on layer  data  Export data • Temporary save your selected features • create a temp layer in your ArcMap project as • Right-click on layer  selection  create layer from selected features • One extra step …. • --- to create a .lyr file • Right-click on layer Save As Layer File

  10. Summary of selection types • Select by attribute using SQL • In ArcMap you can find this in the: • Selection menu • Attribute table • Definition query – displays data only • Located in the layer’s properties • Spatial Query: • Manually using the cursor • Select by graphics • Select by Location dialog

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