1. Mastering ArcGIS
Chapter 7
Queries

2. What are queries? Extract certain records from a map or table
Mastering ArcGIS
Chapter 7
What are queries?
Extract certain records from a map or table
Records meet certain criteria
Aspatial queries
All parcels with value greater than $100,000
Spatial queries
All parcels that lie completely within the flood plain
Copyright © 2009 by Maribeth H. Price

3. SELECT *FROM FIELD WHERE
Mastering ArcGIS
Chapter 7
SQL
Many databases use a special query language called Structured Query Language
SELECT *FROM FIELD WHERE
Copyright © 2009 by Maribeth H. Price 3

4. Mastering ArcGIS
Chapter 7
SQL Query Examples
Some Valid Queries
SELECT *FROM cities WHERE "POP1990" >=
SELECT *FROM counties WHERE “BEEFCOW_92” < “BEEFCOW_87”
SELECT *FROM parcels WHERE “LU- CODE” = 42 AND “VALUE” > 50000
SELECT *FROM rentals WHERE “RENT” > 700 AND “RENT” < 1500
Programs may have an interface to help users build SQL expressions
In most databases, SQL expressions are case-sensitive “Smith” ≠ “SMITH”
Copyright © 2009 by Maribeth H. Price 4

5. Single criteria T A B Select students from T where [Home_State] = “NY”
Mastering ArcGIS
Chapter 7
Single criteria
Let T = [all students in University]
Let A = [students from New York]
Let B = [Geography majors]
Let C = [English majors] T A B
Select students from T where [Home_State] = “NY”
Select students from T where [Major] = “Geography”
Copyright © 2009 by Maribeth H. Price 5

6. Mastering ArcGIS
Chapter 7
Queries as sets
Let T = [all students in University]
Let A = [students from New York]
Let B = [Geography majors]
Let C = [English majors] T A
Queries are used to extract subsets (records) of interest from a set (table)
Multiple criteria may be used (such as Geography majors from New York) B C
Copyright © 2009 by Maribeth H. Price 6

7. Mastering ArcGIS
Chapter 7
Double criteria T
Let T = [all students in University]
Let A = [students from New York]
Let B = [Geography majors]
Let C = [English majors] A B
Select students from T where [Home_State] = “NY” OR [Home_State] = “NJ”
Select students from T where [Home_State] = “NY” AND [Major] = “Geography”
Copyright © 2009 by Maribeth H. Price 7

8. Mastering ArcGIS
Chapter 7
AND vs OR? T A B C
Let T = [all students in University]
Let A = [students from New York]
Let B = [Geography majors]
Let C = [English majors]
Select students from T where [Home_State] = “NY” OR [Home_State] = “NJ”
Select students from T where [Home_State] = “NY” AND [Major] = “Geography”
Each condition is tested separately. If AND is used, then BOTH must be true. If OR is used, then either may be true.
Copyright © 2009 by Maribeth H. Price 8

9. Boolean expressions AND and OR are Boolean operators
Mastering ArcGIS
Chapter 7
Boolean expressions
AND and OR are Boolean operators
Boolean operators are used to evaluate pairs of conditions
Copyright © 2009 by Maribeth H. Price 9

10. Mastering ArcGIS
Chapter 7
AND vs OR? T A B C
Let T = [all students in University]
Let A = [students from New York]
Let B = [Geography majors]
Let C = [English majors]
A AND B
A B
Select students from T where [Home_State] = “NY” AND [Major] = “Geography”
Copyright © 2009 by Maribeth H. Price 10

11. Mastering ArcGIS
Chapter 7
AND vs OR? T A B C
Let T = [all students in University]
Let A = [students from New York]
Let B = [Geography majors]
Let C = [English majors]
A OR B
A B
Select students from T where [Home_State] = “NY” OR [Major] = “Geography”
Copyright © 2009 by Maribeth H. Price 11

12. Mastering ArcGIS
Chapter 7
What do you get? T A B C
Select students from T where [Major] = “Geography” OR [Major] = “English” B OR C
Select students from T where [State] = “NY” AND [Major] = “English” A AND C
Select students from T where [State = “NY” OR [Major] = “English” A OR C
Let T = [all students in University]
Let A = [students from New York]
Let B = [Geography majors]
Let C = [English majors]
Copyright © 2009 by Maribeth H. Price 12

13. Mastering ArcGIS
Chapter 7
What do you get? T A B C
Select students from T where [Major] = “Geography” AND [Major] = English” B AND C
Select students from T where [AGE] > 20 AND [AGE] < 30 ? AND ?
Select students from T where [AGE] > 20 OR [AGE] < 30 ? OR ?
Let T = [all students in University]
Let A = [students from New York]
Let B = [AGE > 30]
Let C = [AGE < 20]
Copyright © 2009 by Maribeth H. Price 13

14. Other Boolean operators
Mastering ArcGIS
Chapter 7
Other Boolean operators
Some databases use additional operators besides AND and OR
A AND B
A XOR B
A NOT B
A OR B
A B
Copyright © 2009 by Maribeth H. Price 14

15. What do you get? T A B C A AND B A OR B A XOR B A NOT B B AND A B OR A
Mastering ArcGIS
What do you get?
Chapter 7 T A B C
A AND B
A OR B
A XOR B
A NOT B
B AND A
B OR A
B XOR A
B NOT A
Let T = [all students in University]
Let A = [students from New York]
Let B = [Geography majors]
Let C = [English majors]
Copyright © 2009 by Maribeth H. Price 15

16. Remember—you test each feature separately
Mastering ArcGIS
Chapter 7
Test: AND vs OR
Remember—you test each feature separately
Wrong
Right
“Land-use” = ‘RES’ AND
“Land-use” = ‘COM’
“Land-use” = ‘RES’ OR
“Land-use” = ‘COM’
“Pop2000” ≥ 5000 OR
“Pop2000” < 9000
“Pop2000” ≥ 5000 AND
“Pop2000” < 9000
Copyright © 2009 by Maribeth H. Price 16

17. Order of operations Boolean operators have equal order or precedence
Mastering ArcGIS
Chapter 7
Order of operations
Boolean operators have equal order or precedence
Evaluation occurs from left to right
Parentheses must be used to change order
Copyright © 2009 by Maribeth H. Price 17

18. What do you get? T A B C A AND B OR C ( A AND B ) OR C A AND (B OR C)
Mastering ArcGIS
Chapter 7
What do you get? T A B C
A AND B OR C
( A AND B ) OR C
A AND (B OR C)
(A OR B ) AND C
A OR (B AND C)
A AND B
A XOR B
A NOT B
A OR B
A B
Let T = [all students in University]
Let A = [students from New York]
Let B = [Geography majors]
Let C = [English majors]
Copyright © 2009 by Maribeth H. Price 18

19. Multiple conditions Test using these parcels RES COM $75,000 $75,000
Mastering ArcGIS
Chapter 7
Multiple conditions
Test using these parcels
$75,000
$75,000
$75,000
$75,000
$125,000
$125,000
$125,000
$125,000
RES
COM
Copyright © 2009 by Maribeth H. Price 19

20. (“LU” = ‘RES’ or “LU” = ‘COM’) and “Value” > 100000
Mastering ArcGIS
Chapter 7
Multiple conditions
Test using these parcels
(“LU” = ‘RES’ or “LU” = ‘COM’) and “Value” >
$75,000
$75,000
$75,000
$75,000
$125,000
$125,000
$125,000
$125,000
RES
COM
Copyright © 2009 by Maribeth H. Price 20

21. “LU” = ‘RES’ or (“LU” = ‘COM’ and “Value” > 100000)
Mastering ArcGIS
Chapter 7
Multiple conditions
Test using these parcels
“LU” = ‘RES’ or (“LU” = ‘COM’ and “Value” > )
$75,000
$75,000
$75,000
$75,000
$125,000
$125,000
$125,000
$125,000
RES
COM
Copyright © 2009 by Maribeth H. Price 21