ch03 access

Analyzing Data For Effective Decision Making

Chapter 3

“The human problems which I deal with every day—concerningemployees as well as customers—are the problems that fascinateme, that seem important to me.”

—Hortense Odlum

XPXPChapter Introduction• Filter data in Microsoft Office Access 2007

database – Retrieve and examine only records you need

• Sort data – Rearrange records in specified order

• Queries– Provide quick answers to business questions

Succeeding in Business with Microsoft Office Access 2007: A Problem-Solving Approach 2

XPXPTools Covered In This Chapter• Action queries (update, append, delete, crosstab,

and make-table)• Aggregate functions (Avg, Max, Min, Sum)• Calculated field• Comparison and logical operators• Crosstab query• Filter by Form and Filter by Selection• Find duplicates query• Find unmatched records querySucceeding in Business with Microsoft Office Access 2007: A Problem-Solving Approach 3

XPXPTools Covered In This Chapter• Immediate IF (IIF) function• Parameter query• Design view• Select query• Simple Query Wizard• SQL commands (AS FROM, GROUP BY, HAVING,

ORDER BY, SELECT, WHERE)• Top Values query• Wildcard charactersSucceeding in Business with Microsoft Office Access 2007: A Problem-Solving Approach 4

XPXPLevel 1 Objectives: Organizing and Retrieving Information from a Database• Filter and sort data to make it more meaningful• Create simple queries to answer business

questions• Develop queries using comparison criteria and

wildcards• Display and print query results

XPXPFiltering and Sorting Data• Filter

– Restricts data in single table to create temporary subset of records

– See only certain records in table based on specified criteria

• Sorting records – Organizing in particular order or sequence– Sort records regardless of whether table filtered

XPXPFiltering by Selection• Tools

– Filter by Selection• Select particular field in datasheet • Display only data that matches contents of field• Specify only one criterion for filter

– Filter by Form

XPXPUsing Filter by Selection to Display a Temporary Subset of Records

XPXPFiltering by Form• Specify two or more criteria• Filter for comparative data

– Use comparison operators• AND criteria

– Selects records that contain all specified values• OR criteria

– Selects records that contain any specified values

XPXPSorting Data to Increase Information Content• Organizes data and increases information value• Access sorts records based on primary key values

– Use sorting to change order• To sort

– Select sort field• Sort on multiple fields

– Move fields in datasheet view so that they are adjacent

XPXPSorting Data To Increase Information Content• Primary sort field

– Access sorts records by this field first

XPXPSorting Types of Data

XPXPFiltering Using the Filter Arrow

XPXPUsing Queries to Answer Business Questions• Query

– Database object – Stores criteria for selecting records from one or more

tables based – Save query

• Use it again

– More powerful than filter• Display only some fields in table• Create fields that perform calculations

XPXPUsing Queries to Answer Business Questions (continued)• Capabilities of Access queries:

– Display selected fields and records from table– Sort records on one or multiple fields– Perform calculations– Generate data for forms reports and other queries– Update data in database– Find and display data from two or more tables– Create new tables– Delete records in table based on one or more criteria

XPXPUsing Queries to Answer Business Questions (continued)• Select query

– Ask question based on one or more tables in database

– Result displayed in datasheet• Called recordset

XPXPUsing the Simple Query Wizard to Create a Query• Simple query wizard

– Presents list of tables and queries in database • And fields that they contain

– Select fields from one or more tables– Wizard creates and displays results

XPXPAdvantages and Limitations of the Simple Query Wizard

XPXPIncluding Summary Statistics in a Query for Data Analysis• Summary query

– Groups records – Calculate sum, average, minimum, or maximum value

in each selected field– Count records in table or query

• Click summary options button

XPXPCreating a Summary Query with the Simple Query Wizard

XPXPCreating a Query in Design View• Select query window in Design view has two

sections – Area for field lists at top of window – Design grid below it

• Add tables for query to top part of window– Appear as field lists

• Query by example (QBE)– Typing search value as a criterion

XPXPQuery Design View Tools

XPXPCreating Queries with Multiple Criteria• Most queries involve more than one criterion• Represent AND criteria

– Entering conditions in same criteria row in query design grid

• Specify OR criteria– Use “or” row of query design grid

XPXPSetting Criteria for the Query in Design View

XPXPSpecifying Sort Order in Queries• Query results appear in same order as data from

underlying tables – Unless specify sort order when designing query

• Sort order determined from left to right• Multiple columns must be adjacent to sort on

more than one field in datasheet view

XPXPRunning a Query• Click Run button in the Results group on the

Design tab– Access displays datasheet of records

• Save query– Save only design– Not values from tables displayed in results

XPXPEnhancing Query Criteria to Improve Data Analysis• Expand criteria by using

– Wildcards – Comparison operators

XPXPUsing Wildcards for Inexact Query Matches• Wildcard character

– Placeholder – Stands for one or more characters

• Memo fields– Use same keywords throughout memos– Easily retrieve records later– Use wildcards when specifying keyword as a query

criterion • To select records that contain characters before and after

keyword

XPXPWildcard Characters Used in Queries

XPXPUsing Wildcards for Inexact Query Matches (continued)• Access inserts

– Word “LIKE” for criteria with wildcards quotation marks around text

• LIKE “*Spanish*”

– Pound signs around dates• #12/*/2008#

XPXPUsing Comparison Operators to Refine Query Criteria• Comparison operators

– Compare value in field with range of values in criterion

• Clear the grid – Start with same field list but blank grid

XPXPComparison Operators

XPXPComparison Operators (continued)

XPXPVerifying and Printing Query Results• Verify query results before

– Distributing query to others – Using it as basis for decisions

• Use business knowledge – Determine whether results adequately answer

question• Print query datasheet

XPXPModifying Query Datasheets• Improve appearance of query or table datasheet• Resize column widths in any datasheet

– Double-click line between field names to resize columns to best fit

XPXPFormatting Options for Query and Table Datasheets

XPXPLevel 1 Summary• Use filtering and sorting to change data display• Develop queries using

– Simple query wizard– Design view

• Use comparison operators and wildcards to make queries more flexible

• Verify query results using business knowledge

XPXPLevel 2 Objectives:Creating More Complex Queries• Design queries that compare data from more

than one table• Refine table relationships by specifying the join

type• Perform calculations in queries• Customize queries and their results

XPXPEvaluating Data Using Special Types of Queries

XPXPUsing Queries to Find Duplicate Records• Duplicates Query Wizard

– Searches for duplicate values in fields– Improve business operations– Designed to identify records that contain same

information in particular field

XPXPUsing Queries to Find Unmatched Records• Find Unmatched Query Wizard

– Compares records in two specified tables or recordsets

– Finds all records in one table or query that have no related records in second table or query

– Requires that two tables being compared have common field

XPXPLimiting the Records in the Query Results• Limiting results to only a few records often aids

analysis• Top and Bottom Values

– Sorts and then filters records – Display specified number of records that contain top

or bottom values– Top Values button on Design tab

XPXPTop Values Query Design and Results

XPXPUsing Parameter Values in Queries• Parameter values

– Phrase usually in form of a question or instruction – Enclosed in square brackets– Serves as prompt to user to enter value– Example

• [Enter a job ID:]

XPXPParameter Query to Allow User Input when the Query Is Run

XPXPAnalyzing Data from More than One Table• Data from more than one table required to

answer question– Combine records from two or more tables – Display only information needed

• Work in design view to specify criteria for selecting records from multiple tables

• Lines between tables link primary key to foreign key field– Primary key designated with 1– Foreign key designated with ∞

XPXPAnalyzing Data from More than One Table (continued)• Join tables

– Linking of tables using primary and foreign keys– Established relationship – Or

• Each table shares field with same or compatible data type • One join field primary key

• If tables do not include fields that can be joined– Add one or more extra tables or queries – Link tables that contain the data

XPXPAnalyzing Data from More than One Table (continued)• Use queries as source of underlying data for

another query in place of one or more tables• Create queries based on more than one object

– Should not use any table or query that does not have common field with at least one of the other tables or queries

– Otherwise Access displays every combination of records between two tables

XPXPRefining Relationships with Appropriate Join Types• Inner join

– Displays all records in one table that have corresponding values in common field in another table

– Records must match before being displayed in query results

• Outer join– Display all records of one table – Regardless of whether corresponding record stored in

related table

XPXPInner Join

XPXPLeft Outer Join

XPXPRight Outer Join

XPXPRefining Relationships with Appropriate Join Types (continued)• Outer join types

– Left– Right

• Use join properties dialog box– To change join type– By default tables related using inner joins

XPXPUsing Logical Operators to Specify Multiple Conditions• Logical operators

– Test values that can only be true or false• Place conditions in separate fields in same

criteria row of design grid– All conditions in row must be met to select record

• NOT logical operator – Excludes values that don’t meet criterion

XPXPLogical Operators

XPXPPerforming Calculations with Queries• Any information derived from fields in table or

query should be calculated in query – Rather than included as data in table

• Calculation types– Predefined

• Compute amounts for groups of records or for all records combined in query

– Custom• Performs numeric date and text computations on each

record • Using data from one or more fields

XPXPCalculating Statistical Information• Aggregate functions

– Arithmetic and statistical operations – Apply to records that meet query’s selection criteria

XPXPAggregate Functions

XPXPUsing Aggregate Functions in a Query

XPXPCreating Calculated Fields in a Query• Expression

– Arithmetic formula used to make calculation– Use standard arithmetic operators– Use parenthesis for complex expressions

• Calculated field– Add to query design grid– Type expression

• Expression builder– Build complex expressions

XPXPCreating Calculated Fields in a Query (continued)• Function

– Perform standard calculation– Return value

• Date()– Provides today’s date

• Field properties– Change format and number of decimal places for

calculated field

XPXPField Properties

XPXPConcatenating in Queries• Concatenation

– Combining contents of two or more fields– Operator

– Example• Name [EmpFirst]& " " & [EmpLast]

XPXPLevel 2 Summary• Use queries to select data from more than one

table• Join types

– Inner– Right outer– Left outer

• Calculated field types– Predefined– Custom

XPXPLevel 3 Objectives: Exploring Advanced Queries and Queries Written in Structured Query Language

• Calculate and restructure data to improve analysis

• Examine and create advanced types of queries• Make decisions in a query using the immediate IF

(IIF) function• Develop queries using SQL

XPXPAnalyzing Query Calculations• Crosstab queries

– Special type of totals query – Performs aggregate function calculations on values of

one database field – Determine exactly how summary data appears in

results– Calculate and restructure data

• Analyze it more easily

– Work especially well with time-series data

XPXPCreating a Crosstab Query• To create use

– Use a wizard• Often need to create query first

– Or design view• Start with select query that includes numeric values or

summary calculations

XPXPCrosstab Field Settings

XPXPModifying Data Using Queries• Action queries

– Modify data in table – Add records to or delete records from table – Create new table

• Backup data before using action query

XPXPAccess Action Queries

XPXPProcess for Archiving Data

XPXPArchiving Data with Make-table Queries• Make-table query

– Creates table from some or all of the fields and records in existing table or query

– Access does not delete selected fields and records from existing table

XPXPAdding Records to Tables with Append Queries• Append query

– Select records from one or more tables by setting criteria

– Add those records to end of another table– Selected records also remain in original tables – Table to which records added must already exist– Also use to bring data from another source into

database

XPXPRemoving Records from Tables with Delete Queries• Delete query

– Removes information from table – Based on specified criteria– All records meeting criteria permanently removed

from table• Create select query first

– Convert to delete query• Cascading deletes

XPXPUpdating Data with an Update Query• Update query

– Changes values of data in one or more existing tables– Create select query first

• Change type to update query

XPXPMaking Decisions in Queries• IF statement

– Tests condition – Takes one action if condition true – Takes another action if condition false

• IIF function– Make if decision– Format

• IIF(condition to test what to do if true, what to do if false)

XPXPCustomizing Queries Using Structured Query Language• Access designed as database management system

(DBMS) for – Small businesses – Or departments within large businesses

• Structured query language– Common query language of most DBMSs– Use to query, update, and manage relational databases

• Create query in design view– Access translates entries and criteria into SQL statements

XPXPCustomizing Queries Using Structured Query Language (continued)• View statements by switching from Design view

to SQL view• SELECT statement defines

– What data query should retrieve from database – How it should present data

XPXPExploring the Components of an SQL Query• Keywords

– Use to construct SQL statements• Most developers place each statement on

separate line – To make SQL code easy to read

XPXPCommon SQL Keywords

XPXPLevel 3 Summary• Action queries

– Make new tables– Append data– Delete data– Update data

• IFF function• SQL

– Use SQL view to edit SQL directly

XPXPChapter Summary• Queries retrieve data from one or more tables

– Action queries update data– Perform calculations– Make decisions using IFF function

• SQL– Used to interact with relational databases– Use SQL view to view/edit SQL statements generated

by Access

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