1. DB Implementation: MS Access Queries

2. MS Access Queries Database Queries What does it do? How does it work?
Core DBA skill → A way of searching for & extracting data from tables
What does it do?
Find target information → Retrieve, Filter, Sort, Aggregate/Summarize
Manipulate data → Add, Change, Delete, Combine (& calculate) data in tables
Assemble/Supply data → for Forms and Reports
How does it work?
Query object  SQL & a dynaset (“live” view of table)
Data changes made in query is reflected in underlying tables
Database Design

3. Access Queries: Views Datasheet view Design View
For displaying the result of the query → Useful for reviewing/validating the query
Design View
For creating/modifying a query via drag & drop GUI
Object Relationship Pane
Add tables/queries
Add fields to the Design Grid
creation: CUSTOMER table
multi-table query:
PRODUCT+SUPPLIER
qrySensless, qrySensible
Design Grid
Sort row → ascending/descending sort
Show row → show/hide fields
Criteria row → apply data filter
Totals row → compute aggregate stats
Database Design

4. Access Queries: Basic Types
Simple Query
Uses a single table/query
To generate a subset (row/column) of a table
Multi-table Query
Joins multiple tables/queries
Joining tables in Query Design does not permanently link tables
Select Query
Selects records that meet given criteria
Criteria row ← Selection Criteria
Parameter Query
Prompts for query criteria values (parameters) to run a dynamic query
Criteria row ← [Query Prompt] (or Search Form control name)
update:
publisher + publication
set Available=No for publisher JimBob Publishing
append
crosstab
how many works each producers produce in each category?
Database Design

5. Access Queries: Sort & Filter
Design View
Sort using the Sort Row
Sort priority is from left to right for multiple sort
Filter using the Criteria Row
AND query ← criteria in a single row
OR query ← criteria in multiple rows
Criteria in a single cell → AND/OR
Query Criteria
Determines which record to include
“expressions” that consist of
Constants (e.g., 2000, “Adams”)
Operators (e.g., >, +, *, AND)
Functions (e.g., DateDiff)
Field references (e.g., [Lastname])
- Gcflearnfree.org -
CUSTOMER
wildcard: tblVoters
Database Design

6. Access Queries: Query Criteria
Date/Time fields
Number fields
Expression
Returns
Between #1/1/15# and #12/31/15#
Dates from 1/1/2015 to 12/31/2015
> #1/1/15#
After 1/1/2015
< Date()
Before today
DateDiff(“yyyy”,Date(),[Birthdate]) > 60
Over 60 years old
DatePart(“m”, [Birthdate]) = 12
Born in December
Expression
Returns
Between 10 and 20
Number from 10 to 20
>= 10
Greater than or equal to 10 10
Equal to 10
Not 10
Not equal to 10
Is Null
No value is entered
In (5,10,15)
Number equal to 5, 10, or 15
Database Design

7. Access Queries: Query Criteria
Text fields
Expression
Returns
In (“John”, “Mary”, “Jane”)
Equal to John, Mary, or Jane
Like “J*”
Starts with “j”
Like “*s”
Ends with “s”
Like “*oh*”
Contains “oh”
Like “[A-C]??”
Starts with A through C and has two more characters
????
Any 4 characters
Len([LastName]) = Val(4)
Any LastName of 4 characters
Right([LastName],2) = “es”
Any LastName ending in “es” (same as Like “*es”)
Left([LastName],2)= “Ja”
Any LastName starting with “Ja” (same as Like “Ja*”)
Is Null
No value is entered
Is Not Null
Value is not missing
Not “James”
Not equal to “James”
Database Design

8. Access Queries: Expressions
Using expressions to create a Calculated Field
Enter expressions in blank column of query design view
NAME: [Field1] operator [Field2]
Examples
Simple math
DiscountPrice: [Discount] * [StandardPrice]
String Concatenation
Author: [FirstName] & “ ” & [Lastname]
Date & Time math
HireAge: DateDiff(“yyyy”,[BirthDate],[HireDate])
DateDiff(Interval, BeginDate, EndDate)
RetireDate: DateAdd(“yyyy”,25,[HireDate])
DateAdd(Interval, Number, Date)
Customized Sorting/Format
Branch: Switch([City]=“Seattle”, 1, [City]=“Redmond”, 2, [City]=“New York”, 3)
Switch(expr1, value1, expr2, value2, etc.)
tbleCustomerDiscounts + tblPrices
add Cname, discount, Stdprice
Zoom Window (Shift+F2)
Dolla Discount: [Discount]*[StandardPrice]
Net Price: [Standardprice]-[dolla discount]
new Q:
add EMPLOYEE
create name field
Hireage: DateDiff(“yyyy”,[BirthDate],[HireDate])
Database Design

9. Access Queries: Sort & Filter
Datasheet View
Common Filters → Filter for specific values
Click the icon on the right side of the field label
Check the values for the filter OR
Click the Range Filter (e.g. Date Filter) & specify the filter value
Filter by Selection → Filter by selected value
Select a specific value in the datasheet
Right-click & select a filtering option
CUSTOMER
wildcard: tblVoters
Database Design

10. Access Queries: Sort & Filter
Datasheet View
Filter by Form
→ Filter on several fields on a form
Click Advanced in Sort & Filter group of Home tab
Select Filter by Form
Select multiple filter values as needed
Advanced Filter
→ Define custom filters → Learn how to write query criteria
Create a filter by Common Filter, Selection, or Form
Select Advanced Filter/Sort
CUSTOMER
wildcard: tblVoters
Database Design

11. Access Queries: Dynamic Criteria
Parameter Queries
Dynamic query based on varying criteria value
Enter the parameter name in square brackets in criteria
Do not use existing field names
Can use expressions → e.g. Like "*" & [Last Name] & "*“
Database Design

12. Access Queries: Dynamic Criteria
Query Criteria from Form Entries
Use a form to enter query parameter values → good for multiple parameter entries
Create a parameter query
Create a search form with unbound input control for each of query parameters
Add a command button that will run the parameter query
Run Query Action of Miscellaneous Category
Change the query criteria to search form control names
Database Design

13. Access Queries: Joins Inner Join Outer join
Default join in Access (i.e. Natural Join)
Returns only the records where joined fields are equal in both tables
Outer join
Returns all records from one of the tables
Theta Join: CHARTER & MODEL
Database Design