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Access 2002
What We Have Learned
Chapter 4
REVIEW
Chapter 4 deals with some of the critical issues that go into way a database is actually used in
production. Once users have begun to depend upon their database, they find that there are new
questions that questions that need to be asked of the data. No matter how good the original
design, changes must take place and this chapter has dealt with adding, modifying, and deleting
fields. In addition, the data that enters the database should be as “clean” as possible. Input masks
and table lookups can assist the user in entering the correct data the first time.
Finally, it is important that preventative maintenance be performed on the database. The database
needs to be backed up on a regular basis. Compression of the database should be done regularly
to assure that the database is performing as efficiently as possible. In the situation where the
database is damaged somehow, the user has to be able to repair the damage.
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Access 2002
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Access 2002
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Chapter 4
QUESTIONS:
1. What are some uses of compound queries?
Discussion
2. Differentiate among the conditional operators Between, In, and Like?
Discussion
3. Differentiate among the logical operators And, Or, and Not?
Discussion
4. What is the purpose of a Crosstab Query?
Discussion
5. How does a Memo field differ from a Text field?
Discussion
6. Under what circumstances would one use a Lookup field?
Discussion
7. What is the purpose of an Input Mask?
Discussion
8. Why is Compacting a Database useful?
Discussion
9. Under what circumstances should you consider Repairing a database?
Discussion
10. Under what circumstances would it be necessary to convert a database to Access2002?
When should you not convert a database? If you do not convert an older version of the
database, what limitations do you face?
Discussion
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Discussion for Question 1
Compound queries allow the user to use several conditions in seeking data. Thus, complex
queries can be generated. These queries can serve as the basis for sophisticated reports. The
user can develop the analysis in the form of a query and then create the report from the
query. The Reports Wizard has analysis tools of its own, but more sophistication can be
achieved if the data is pre-processed through a query.
Return to Questions.
Discussion for Question 2
Like, In, and Between are all conditional operators and allow more capability than the simple
Less Than, Greater Than, and Equal To operators. Each of the new operators provides for a
range of possible answers.
The Between operator defines both an upper and lower limit to a range of values. It is an
expansion on the >, <, and = operators. In effect, the user can specify that the value must be
greater than some value and less than another value.
The In operator allows the user to establish a set of requested values. If the value can be
found in that set, it will be returned. Having a set of values allows great flexibility in what
data is to be returned.
The Like operator allows retrieval based on partial conditions. This operator can be very
useful for narrowing down a search and providing candidates for the desired record.
Return to Questions.
Discussion for Question 3
And, Or, and Not are logical operators. They are used to combine multiple conditions together to
create a complex expression. And is the most restrictive of these operators. Both sides of the
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Access 2002
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Access 2002
What We Have Learned
Chapter 4
condition must be true for the entire expression to be true. The Or operator considers the entire
expression to be true if both sides are true or either side is true. Only if both sides of the
expression are false does the Or operator treat the condition as false.
Return to Questions.
Discussion of Question 4
Crosstab queries allow the analysis and summarization of a value across two variables. The
Crosstab query can add, count, find an average, and summarize data in several other ways. All of
this serves to provide sophisticated analysis tools for the user.
Return to Questions.
Discussion of Question 5
Both Text and Memo fields contain words and letters rather than numbers. However, Text fields
have a fixed length. This limitation means that only a limited number of characters can be
entered into the field. On the other hand, Memo fields have a variable length. Therefore, any
number of characters can be entered into a Memo field. However, Memo fields cannot be readily
searched. Thus, you cannot perform queries based on the values in a memo field.
Return to Questions.
Discussion of Question 6
Lookup fields are very useful for prompting the user to enter the proper value into a field.
Lookup fields allow the user to select a value from a drop-down list and by clicking make the
entry. This facility reduces the amount of keying for the user and also assures that there are not
keying errors in the data entry.
The lookup values can come from specific values entered by the developer of the database or
may come from another table in the database.
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Access 2002
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Access 2002
What We Have Learned
Chapter 4
Return to Questions.
Discussion of Question 7
Input masks along with lookup fields provide ways of controlling the quality of data that enters
the database. A mask is a format that the user can follow in entering data. Masks can also limit
the actual type of data that can be entered, and can specify how many characters have to be
entered.
Return to Questions.
Discussion of Question 8
Compacting a database means that unnecessary entries are removed and the remaining items are
reorganized into a smaller space on the hard disk. Compacting, therefore, makes more efficient
use of disk storage and also helps the database to run faster.
Compacting should be done on a regular basis for databases that have high utilization and where
a lot of maintenance is performed on the records. Deleted database records are not removed
immediately and consequently the database must work around them. Compacting the database
removes deleted records and updates the indexes.
Return to Questions.
Discussion of Question 9
Under some circumstances the files in a database may become corrupted. Corrupted files, at
worst may not be accessible at all, and at best can produce strange results. One common
occurrence which may corrupt files is when a power failure causes the hardware to shut down
before the database can be closed properly. Under such circumstances the open transactions may
not be stored properly in the database and indexes may not be properly updated.
Arthur R. Buss
Access 2002
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Access 2002
What We Have Learned
Chapter 4
Access is sometimes able to detect when the database needs to be repaired. You should certainly
choose to have the repairs made under this circumstance.
Compacting the database also includes making repairs. Therefore, if there is a procedure in place
to regularly compact the database, this should also take care of any file corruption that is
necessary.
One should not rely entirely on the repair process to keep databases safe from corruption. In
some cases, the damage may be so severe it cannot be repaired. Therefore, there should be a plan
for making backup copies of the database on a regular basis.
Return to Questions.
Discussion of Question 10
Access databases have been improved over the years to incorporate additional features and
performance characteristics. As a result, Microsoft has had to change the file formats of the
Access tables. Microsoft has attempted to keep the new versions of Access compatible with the
older versions. This relationship is one-way, however. The newer versions of Access can process
databases in older formats, but, the older versions of Access cannot process the newer formats.
Thus, there can be a dilemma when a database needs to be processed by users with differing
versions of Access. The database files must be maintained in the earliest version currently being
used. The additional capabilities possessed by the newer versions are not available when this
situation occurs.
When the capabilities and performance characteristics of Access 2002 are critical, the databases
should be converted to that format. The negative aspect is that all users must upgrade their
Access software as well.
Return to Questions.
Arthur R. Buss
Access 2002
ACWL 4.6
<Au 1st draft>
6/28/2017
Access 2002
What We Have Learned
Chapter 4
PRACTICE EXERCISE
We want to use the power of Access to provide Joe with the information he needs. In the Getting
Started section you modified the database to add a Fruit Type to the Fruit Table. We are going to
take advantage of that field to build Crosstab queries.
Building a Total Profit Crosstab Query
1. Make sure Fruit-M-N.mdb is open and located in the Queries object.
2. Click New and select the Crosstab Query Wizard
3. Set the Inventory query as the base table for this query. See Figure ACWL04.1?
Figure ACWL04. 1 Establishing the Base for a Crosstab Query
4. Click Next. Select Fruit Type for Row Headers.
Arthur R. Buss
Access 2002
ACWL 4.7
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What We Have Learned
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5. Click Next. Select Vendor Name for Column Headers as in Figure ACWL04.2.
Figure ACWL04. 2 Setting Row and Column Headers
Arthur R. Buss
Access 2002
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What We Have Learned
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6. Click Next. Select Total Value as the calculated field and Sum the values. Your screen
should look like Figure ??.
Figure ACWL04. 3 Establishing the Sum of TotalValue for the Calculated Fields
7. Click Next. Name the query Total Value Crosstab. Click Finish. The results of the query
should look like Figure ACWL04.4.
Figure ACWL04. 4 Results of the TotalValue Crosstab Query
Arthur R. Buss
Access 2002
ACWL 4.9
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6/28/2017
Access 2002
What We Have Learned
Chapter 4
Building a Profit Crosstab Query.
You should have enough information to build a Profit crosstab query on your own. Follow the
procedure described for the Total Value Query. However, this time use VendorName for the
Row Headers and FruitType for the Column Headers. Sum the Profit field. The result of your
query should look like Figure ACWL04.5.
Figure ACWL04. 5 Results of Profit Crosstab Query
Building Reports for the Crosstab Queries.
Joe would like to see the crosstab information in the form of printed reports rather than just the
table format. We will step through the report wizard for the first report and you can build the
second report on your own.
1. Open the Fruit-M-N.mdb database in the Reports Object.
2. Created a new report using the Report Wizard. Use Total Value Crosstab as the base table
for the report.
Arthur R. Buss
Access 2002
ACWL 4.10
<Au 1st draft>
6/28/2017
Access 2002
What We Have Learned
Chapter 4
3. Select all fields into the report. At this point, your work should look like Figure
ACWL04.6.
Figure ACWL04. 6 Selecting Fields from a Crosstab Query for a Report
Arthur R. Buss
Access 2002
ACWL 4.11
<Au 1st draft>
6/28/2017
Access 2002
What We Have Learned
Chapter 4
4. Click Next and select Fruit Type as the grouping level. The resulting window should look
like Figure ACWL04.7.
Figure ACWL04. 7 Adding FruitType as a Grouping Level for the Report
5. Click Next and then Summary Options. Select Sum for all of the fields and Show the
Summary Only. The results should look like Figure ACWL04.8. Click OK to return to
Arthur R. Buss
Access 2002
ACWL 4.12
<Au 1st draft>
6/28/2017
Access 2002
What We Have Learned
Chapter 4
the previous window.
Figure ACWL04. 8 Setting the Calculations to be Performed.
Arthur R. Buss
Access 2002
ACWL 4.13
<Au 1st draft>
6/28/2017
Access 2002
What We Have Learned
Chapter 4
6. Click Next and change the report Orientation to Landscape. Figure ACWL04.9 shows
the settings.
Figure ACWL04. 9 Setting the Format of the Report
7. Click Next. Pick a style of your choosing, and then click Finsh to see the results.
Arthur R. Buss
Access 2002
ACWL 4.14
<Au 1st draft>
6/28/2017