1. Nagendra Vemulapalli Nagendra.vemulapalli@mail.wvu.edu
Access chapters 1&2
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2. Announcement Lesson C in MyITLab is due on 03/18/2013 7/27/2019
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3. Get the Database
Download and open Example1 file from todays lecture notes
* Premise: We are running a company and this database tracks information on our employees
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4. Filters Give a temporary view of desired data to help isolate portions
Filter by Selection – lets us specify an example
Filter by Form – more powerful, can search for records meeting multiple conditions and by operators such as: <, >, <=, >=
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5. Filter by Selection Example
Say we wish to isolate our employees with poor performance…
Open the Employees table
Click in one of the field values containing Poor
Click Selection in the Sort & Filter group
Select Equals Poor
Click Toggle Filter to turn off
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6. Filter by Form Example
Say we want to see all Females making over $40k…
Select Advanced in Sort & Filter group
Choose Filter By Form
Remove Poor from performance
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7. Filter by Form Example Select F for Gender Enter >40000 for Salary
Click the Toggle Filter button
Review the results
Toggle the filter off
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8. Sorting on a Single Field
Sorting allows us to arrange the way the table data looks…
Click in a record under the Last Name field
Click the Sort Ascending button
Next, sort ascending on Salary
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9. Sorting on Multiple Fields
Fields must be side by side to do this
Click and Drag to highlight both the LastName and FirstName fields
Sort Descending (Note the Smith’s first names)
Do it again Ascending
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10. Databases & Relationships(Lookahead.accdb)
A Database is a collection of “Related” tables
This can also be called a “Relational Database”
A Common Field between tables is what allows a relationship to exist. This works by way of “Primary” and “Foreign” keys…
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11. Primary Keys
Primary Key – Field in a every table whose field values are unique for every record
Examples might be things like:
Student ID numbers
SSN number
Cell Number
Anything that will not have duplicates as additional records are entered
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12. Relationships
Foreign Key – Similar/Same field in the second related table in the relationship
Primary key field in relationship will have similar data type and content to foreign key field
The two tables are joined together on the primary and foreign keys and form a Common Field.
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13. Relationships
The link formed through this Common Field which is dubbed in one case as a “primary key”, and in another as a “foreign key”, allows tables to share data
Note that the “Look Ahead” database has 3 tables, but we will only look at 2 of them..
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14. 1: Employees Table…
EmployeeID is the Primary Key as all numbers are unique for employee records
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15. 2: Locations Table…
LocationID is the primary key and each record has a unique LocationID designator.
This will tie back to the Employees table.
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16. Relationships
Databases are all about efficiency and not having to store the same information more than once if multiple records need it
In this example, we know that multiple people work at the same office address. One address can have many related Employees (One to Many)…
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17. Relationships
Instead of typing the same address in each record for every Atlanta office employee: “450 Peachtree Road…”
We can assign a simple relationship to a “Locations” table and reference this information to a given location with a short common code of “L01” between the tables…
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18. One to Many Relationship
(One instance here)
(Many here)
Typing “L01” when entering an employee and having it equate to the entire address saves MANY characters in databases as it is reused over and over.
“L01” is 3 characters and the entire address is over 30 !
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19. Making the Relationship
These tables need to be tied together (related) to work this way…
Open the Relationships Window
Database Tools ribbon > Relationships
Click Show Table
Double click Employees & Locations, then Close
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20. The Relationships Window
The Relationship window depicts included table structures and their associations
Within the structures, we see each table’s fields
Primary keys are shown with a key icon …
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21. Making the Relationships
Drag “LocationID” from the “Locations” table to “LocationID” in the “Employees” table.
Notice the “One-To-Many” reference
Click to Enforce Referential Integrity
Click Create…
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22. Relationship Formed (Relationship Primary Key)
Note the One to Many
(1 to infinity symbol) that formed on the join line…
Close and save the relationship
Run the “Employee Information” query to see data pulled together from both tables…
(Relationship Foreign Key)
Note, the relationship we made was already created in the query we ran and we did this only for increased understanding of how to create relationships.
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23. Query Results
Information is pulled from the “Employee” and “Locations” tables through their relationship and shown united within the query results to give us a complete picture of the information !
The LocationID field was used behind the scenes to pull it all together with the L01 value
The full address is actually only stored (taking up space) once in the database, and we are able it multiple times as needed.
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