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DB Implementation:
MS Access Queries
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Outline
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Access Queries
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Query Creation
Sorting & Filtering
Query Types
Dynamic Query
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MS Access Queries
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Database Queries
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Core DBA skill
From SQL to Query by Example (QBE)
What does it do?
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Find target information
• Retrieve, Filter, Sort, Aggregate/Summarize
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Manipulate data
• Perform calculations
• Add, Change, Delete, Combine data in tables
• Assemble/Supply data for forms and reports
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How does it work?
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Access translates QBE to SQL
SQL performs data manipulations based on Relational Algebra
Access queries create a dynaset (“live” view of table)
• changes made in data by query is reflected in underlying tables
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Access Queries: Views
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Datasheet view
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For displaying the result of the query
Useful for reviewing/validating the query
Design View
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For creating/modifying a query using drag & drop GUI (i.e., QBE)
Consists of Diagram Pane & Grid Pane
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Can sort/filter/compute by fields
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Add tables/queries to the Diagram Pane
Add fields to the Grid Pane (Field row)
Sort row: set to Ascending/Descending
Criteria row: use Expression to apply data filter
Total row: compute (sum, min, max, count, etc.) of each field
Automatically generates SQL statements
SQL View
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For creating/modifying a query by manually writing SQL statements
Only way to create SQL-specific queries
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Union/Data-definition/Pass-through query
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Access Queries: Basic Types
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Simple Query
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Uses one table/query
To generate a subset (row/column) of a table
Multi-table Query
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Joins multiple tables/queries
To merge small chunks of data in normalized tables
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Select Query
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Linked tables are automatically linked in in the Query Design Grid
Creating a link in the Query Design Grid does not permanently link tables
Selects records that meet given criteria
Does not change the data
Parameter Query
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Prompts for query criteria values (parameters) to run a dynamic query
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Access Queries: Sort & Filter
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Datasheet View
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Sorting
• Click column and right-click
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Filtering
• Filter Tool (Home tab)
 Filter by Selection
 Filter by Form
 Advanced Filter/Sort
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Design View
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Sort using the Sort Row
• Sort priority is from left to right for multiple sort
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Filter using the Criteria Row
• Criteria in multiple rows make OR query
• Criteria in single row make AND query
• Criteria in a single cell
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AND/OR
Wildcards (*) in Like and Between
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e.g. Like “A*”, Like “[A-C]*”, Like “*av*”, Like “ave?”, Not Like “A*”
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e.g. Between 1950 and 1960, >1960
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Access Queries: Query Criteria
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Query Criteria Expressions
Expression
Returns
Between #1/1/99# and #12/31/99#
Dates from 1/1/99 to 12/31/99
In (“John”,”Mary”,”James”)
Records with John, Mary, or James
Is Null
Records with no entry
Like “Acc?ss”
‘Acc’ followed by any character, followed by ‘ss’
Like “*s”
Ends in ‘s’
Like “v*”
Starts with ‘v’
<1000
Less than 1000
1000
Equal to 1000
Like “[A-C]??”
Starts with A through C and has two more characters
????
Any four characters
Len([Surname])= Val(4)
Any Surname of 4 characters
Right([Surname],2)= “ss”
Any Surname ending in “ss”
Left([Surname],2)= “ac”
Any Surname starting with “ac”
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Access Queries: Expressions
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Using expressions to create a calculated column
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Enter expressions in blank column of query design view
• NAME: [Field1] operator [Field2]
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Format the display in Format property of the field
Examples
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Simple math
• DiscountPrice: [Discount] * [StandardPrice]
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String Concatenation
• Name: [FirstName] & “ ” & [Lastname]
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Date & Time math
• DateDiff(Interval, BeginDate, EndDate)
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HireAge: DateDiff(“yyyy”,[BirthDate],[HireDate])
• DateAdd(Interval, Number, Date)
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RetireDate: DateAdd(“yyyy”,25,[HireDate])
Customized Sorting
• Switch(expr1, value1, expr2, value2, etc.)
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Switch([City]=“Seatle”, 1, [City]=“Redmond”, 2, etc.)
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Access Queries: Dynamic Criteria
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Parameterized Queries
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Dynamic query based on varying criteria value
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e.g. retrieve books written by a given author
Enter the parameter name in square brackets in criteria
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Do not use existing field names
Can use expressions
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e.g. Like "*" & [Last Name] & "*“
Query Criteria from Form Entries
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Use a form to enter query parameter values
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good for multiple parameter entries
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Create a parameter query
Create a form with unbound input control for each of query parameters
Add a command button that will run the parameter query
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Run Query Action of Miscellaneous Category
Reference the form controls that hold parameter values from the query
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i.e. change the criteria to form controls
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Parameter name = fully qualified name of form control
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Access Queries: Joins
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Inner Join
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Left Outer join
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Default join in Access (i.e. Natural Join)
Returns only the records where joined fields are equal in both tables
Returns all records from the left table
Right Outer join
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Returns all records from the right table
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Access Queries: Advanced Types
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Action Queries
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Append Query
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Delete Query
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Creates a new table from rows of other tables/queries
 will overwrite existing table of the same name
Crosstab Query
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Modifies the values of particular fields for particular records
Make Table Query
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Deletes table rows
Update Query
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Appends table rows to an existing table
Performs mathematical operations on intersection of two fields
SQL-Specific Queries
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Data-definition Query
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Union Query
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Defines/Changes the definition of a database object (e.g., create/modify a table)
Combines multiple SELECT queries
Pass-through Query
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Send command directly to ODBC database server to run server-side SQL
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Access Queries: Action Queries
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Append Query  Appends table rows to an existing table
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Create a select query.
Convert the select query to an Append query
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Choose the destination fields for each column in the append query.
Run the query to append rows/records.
Delete Query  Deletes table rows
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Create a select query.
Convert the select query to a Delete query.
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Delete Tool in Query Type group of Design tab
Run the query to delete rows/records.
Update Query  Modifies the values of particular fields for particular records
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Create a select query.
Convert the select query to an Update query.
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Append Tool in Query Type group of Design tab
Update Tool in Query Type group of Design tab
Set Update To: (and Criteria when appropriate) rows
Run the query to update fields/columns.
Make Table Query  Creates a new table from rows of other tables/queries
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Create a select query.
Convert the select query to a Make Table query.
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Make Table Tool in Query Type group of Design tab
Run the query to update fields/columns.
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Access Queries: Crosstab Query
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Crosstab Query  Performs mathematical operations on intersection of two fields
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Using the Crosstab Query Wizard
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Create a select query to join tables (if needed).
Click Query Wizard in the Other group of the Create tab.
Select Crosstab Query Wizard in the New Query dialog box & click OK.
Choose table/query with which to create a crosstab query & click Next.
Choose the field(s) whose values will be used as row headings & click Next.
Choose the field whose values will be used as column headings & click Next.
Choose a field and a function to use to calculate summary values.
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The data type of the field that you select determines which functions are available.
Using the Crosstab Tool
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Create a select query.
Convert the select query to a Crosstab query
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Set Row Headings
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Crosstab = Column Heading, Total = Group By
Set the calculation field and function
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Crosstab = Row Heading, Total = Group By, Sum, Avg, etc.
Set Column Headings
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Crosstab Tool in Query Type group of Design tab
Crosstab = Value, Total = Sum, Avg, etc.
Set Criteria to filter data (if needed).
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Total = Where, Criteria = expression
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Access Queries: SQL Queries
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Data-definition Query  Defines/Changes the definition of a database object
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Create a table
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Modify a table
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ALTER TABLE table_name
ADD/ALTER COLUMN field type(size)
DROP COLUMN field
Union Query  Combines multiple SELECT queries
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Select queries must have the same fields (i.e., Union compatible)
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CREATE TABLE table_name
( field1 type(size), field2 type(size), … , PRIMARY KEY (field))
SELECT field1, field2, …. FROM table1
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SELECT fieldA, fieldB, …. FROM table2
Create the select queries in Design view
Copy & paste SQL statements into a union query
Pass-through Query  Send command directly to ODBC database server to run server-side SQL
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Configure the server DBMS as an ODBC data source
Create a Pass-through query
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