Module 7 Flashcards
Joined Vs. Related
Join:▪ separate tables can be joined based on the unique identifier, which is shared between each table – in this case the two tables are combined into a new table that contains all of the information of the two separate tables
-▪ joins are very useful for incorporating standalone tables into a GIS analysis
Related:▪ separate tables can be related based on the unique identifier, such that when you select a specific feature in one table, the associated records in the 2nd table are also selected
Standalone Tables
▪ standalone tables often do not have explicit spatial coordinate variables, so they cannot be mapped - they contain attribute data but no feature data
direction
.you must correctly choose which table to add the 2nd table to
▪ the destination table is the table that will accept the additional attribute data from the other table
▪ the source table is the table containing the information you want to add
-it is important that the destination table contain spatial features so that the newly joined data can be mapped – if you make a standalone table the destination table, there will be no way to map the data
many types of relationships between tables, and these are defined by their cardinality: 4 describe each
- one-to-one cardinality
- one record in table 1 corresponds with 1 record in table 2 (eg, one table contains census tracts, the other contains unemployment rate) - one-to-many cardinality
- for every record in table 1, there are several records in table 2 (eg, one table contains all of the national parks in Canada, the other table contains individual lakes found in national parks – each national park may have more than 1 lake) - many-to-one cardinality
- each record in the source table could fit into more than one record in the destination table (eg, a table listing the properties of major highways is joined to a table containing city boundaries) - many-to-many cardinality
- several records in 1 table can be related to many records in another table (eg, different soil types can grow more than one type of crop, and different crops can grow in different soil types)
Rule of Joining****
there must be one and only one record in the source table for each record in the destination table
-this rule is broken by the “many to one cardinality”
we can’t use a join in a many-to-one relationship, but we can use a ______
many-to-many relationship cannot be joined – the most effective way would be to establish several…
relate
many-to-one relationships from the data and then create multiple relates to bring them all together
DBMS
tool to find the aspatial data and where it is stored
the ______ in ArcGIS is the primary tool
for database management
Catalog
3 main Steps in using a Data Management System
- Data Entry
- Verification(checking data vs. original source)
- Updates
multiple membership
where an individual can
exist in more than one group and potentially at more than one level
______ data structure cannot handle multiple membership data connections
hierarichal
relational databases
relational databases are one of the paradigm shifts
that redefined how DBMS’s could be built
▪ the relational model uses many tables that contain
unique levels of attribute data, but the individuals in
the tables are linked by some unique identifier
GIS Summarize function
▪ the summarize function is useful for performing
statistical analysis on groups of data
in a raster the count field in the atribute table is..
a count field that displays how many raster cells are of each code – the count field can be thought of as an area field as well, since you know the cell dimensions (eg, 30 x 30 m)
clip and erase tools
clip would keep everything within the clip shape
erase would erase everything within the shape
object-oriented database
the object-oriented database allows the user to specify both the structure of the objects and the processes that can be applied to them, such that:
▪ the ‘state’ of an object is the set of values of its attributes, and the ‘behaviour’ represents how those attributes might change
.object-oriented databases are potentially more appropriate for geographic data
than the relational model, since they allow for the modeling of complex, real-world
objects, does not distinguish between spatial and attribute data, and is appropriate
for graphics operations
The ______ database type is the best for GIS because…3
.object-oriented databases are potentially more appropriate for geographic data
than the relational model, since they allow for the modeling of complex, real-world
objects, does not distinguish between spatial and attribute data, and is appropriate
for graphics operations
– the packaging together of the description of state and behaviour
in each object
– the ability to re-use some or all of the characteristics of one object
in another object
– the specific implementation of operations like draw, create, or
delete for each object
faults of the object oriented databases
▪ since many geographic ideal have implicit uncertainty and the spatial objects
that we require our databases to model are often the products of interpretation
or generalizations, it can be difficult to represent the world as rigidly bounded
objects
▪ the methods of creating object-oriented models are in their infancy and much
work is need to simply implement them, either practically or theoretically
