1. Designing a Databases
“A database is a collection of logically related data that can be organized
and accessed quickly. The data can be stored in form of text, number or
graphics and can be searched, retrieved and accessed quickly.”
Before actually creating a database, it is extremely important to design
it. It involves creating a 'Conceptual model' of the database.
This can be considered to be a "blue-print", based on which the database
will be created later. The model should be designed such, that the
database should be able to satisfy the current as well as the future
information needs of the organization in picture.
The database designer would have to bear in mind the fact that this
conceptual model should not be dependent on the database model
(whether hierarchical, network or relational).
In addition to this, the model should also be independent of the RDBMS
being used.
While designing a database, several approaches can be taken. The one that we
will be working on is referred to as the 'Entity Relationship model, or the 'E-R
model'. We will be designing our database on the 'E-R model', using which an
E-R diagram can be drawn, which represents the conceptual model of the
database.
Database- A Collection of Interrelated Tables:
A table, is a set of related records arranged in rows and columns.
Table is a basic building block of the database.
A database consists of several tables, each storing a set of related data.
The tables in a database are interrelated.
EXAMPLE:Consider a database that stores data related to an 'Airlines Reservation
System'. The details of the passengers who have booked their tickets
could be stored in the 'Reservation' table, while the details of
cancellations could be stored in the 'Cancellation' table. The date and
timings of the flights could be stored in yet another table. The fare list
could also be stored in another table. All these tables being related to
Airlines reservation could be ideally and appropriately stored in one
database, say the 'Airlines' database.
Consider the example of a Book library. Some of the details that would
need to be recorded are:

2. 1. Details of new books that are added to the Library.
2. Details of books that are lost or never returned to the Library.
3. When a book is issued out to a member, the date, the member code and
book code need to record.
4. Details of members need to be maintained.
5. Members who do not return books within a stipulated time are fined, and
these details are also to be noted down.
6. The rate of each new book that is bought, as well as the charges for
transporting these books have to be recorded.
7. The leave details of the staff have to be maintained.
8. Assuming that there are three librarians who work in shifts and about four
other staff members. Their personal data has to be maintained too.
Understanding Data Types
In Access, you use data types to specify the type of data each field can
capture.
Data Types
Data Type
Text
Memo
Number
Use
Alphanumeric data.
Use for text and for
numbers that are not
used in mathematical
calculations. Use for
names,addresses,
and
other
relativelyshort pieces
of text. Can store
upto 255 characters.
Long text. Use for
long pieces of text,
such as notes and
long descriptions. Can
store up to 64,000
characters.
Numeric data. Use for
numbers you want to
use in mathematical
Notes
If
you
workingwith
currency,
are
usethe

3. Date/Time
Currency
AutoNumber
Yes/No
Hyperlink
calculations.
currency type.
Use for dates and
times.
Use for currency.
Prevents
rounding
during calculation.
Unique
sequential
numbers or random
numbers
automatically
inserted when you
create arecord. Use
to
create
a
primarykey.
Logical data. Use
when only one of two
values
is
valid.
Yes/No,True/False,
etc.
Use
to
store
hyperlinks.
Attachment
Use
to
attachments.
store
OLE Object
Use to attach an OLE
object suchas a Word
document,
Excel
spreadsheet,
or
PowerPoint
presentation.
Specifying the Field Size:
Along with the data type for a field, we can need to specify the field size
if the data type specified happens to be text or Numeric. Specifying the field
size gives the maximum amount of data that can be stored in the field. In
some cases field size need not to specified, e.g. Date automatically set to 8
bytes.

4. Setting
Byte
Integer
Long
Integer
Single
Double
Description
Stores numbers from 0 to 255.
Stores numbers from -32768 to 32767
Default settings; Stores numbers from –2,147,483,648 to
2,147,483,647.
Stores Fractions with a decimal precision of 7 digits.
Stores Fractions with a decimal precision of 15digits.
Tables
In Access, data is stored in tables.
A table is a set of columns and rows, with each column referred to as a
field.
Each value in a field represents a single type of data.
Each row of a table is referred to as a record.
Modify a Table
After you create a table, you may need to modify it. You can delete columns,
insert columns ormove columns.
Delete Columns
The Delete option permanently deletes columns and all the data contained in
them. You cannot undo a column delete.
To delete columns:
1. Click and drag to select the columns you want to delete.
2. Activate the Datasheet tab.
3. Click Delete in the Fields & Columns group. A prompt appears.
4. Click Yes. Access deletes the columns you selected.
Keys:
When we worked with creating a table, we came across the concept of
'Primary Key'. A 'key' is a field or column in a table that is used to identify
records.
Primary Key:
A ‘Primary Key' is a field or a group of fields that uniquely identify
records in a table. It ensures that each record is unique. The 'Primary Key' for
a table can be assigned when the table is created itself. In the 'Customer' table,
for example, every customer has a customer code that can never be
duplicated. In other words, the customer code is always unique. This field
ensures that every record in a table is unique. Such a field is usually assigned

5. as the 'Primary Key'. Although, it is not mandatory that a 'Primary Key' be
assigned to every table. Every table can have only ONE Primary Key.
Foreign Key:
This is a field in a table that refers to a 'Primary Key' field in another
table. Consider the example of the relationship between the 'Customer' and
'OrderMaster' table.
The 'Ccode' field in the 'Customer' table is a 'Primary Key', while the
'Ccode' field in the 'OrderMaster' Ij table is not. When we set a relationship
between these two fields, the 'Ccode' field in the 'OrderMaster' table is said to
be a 'Foreign Key'. This field in the 'OrderMaster' table can only have values
that already exist in the 'Ccode' field of the 'Customer' table. A 'Foreign Key'
can therefore be defined as a copy of a primary key in another table.
The table, which has the ‘Primary Key’ field, is referred to as the
'Master' table, while the related table which has the 'foreign key' field is
referred to as the 'Detail' table.
A 'Foreign Key' can have a Null Value.
Sorting, Filtering, and Creating Relationships
You can sort Access data so you can view records in the order you want
to view them, and
You can filter data so you only see the records you want to see.
Access data is stored in multiple tables.
Relationships join tables together so you can work withthe data from
multiple tables..
Sort a Table
By sorting, you can put a column of information in alphabetical,
numerical, or date order.

6. You can sort in ascending order (alphabetical from A to Z, lowest
number to highest number,earliest date to latest date) or descending order
(alphabetical from Z to A, highest number to lowest number, latest date to
earliest date).
You can also sort within a sort. For example, you can sort by state and
then sort within each state by city. When sorting within a sort, performthe
innermost sort first. For example, if you are sorting by state and then city, sort
the city firstand then sort by state.
To add a sort:
1. Click the column label for the column you want to sort.
2. Activate the Home tab.
3. Click the Ascending or Descending button in the Sort & Filter group.
Access sorts thecolumn in ascending or descending order.
To remove a sort:
1. Activate the Home tab.
2. Click the Clear All Sorts button in the Sort & Filter group. Access clears all
of the sorts youhave applied.
Filter a Table
You can apply a filter to see only the records you want to see.
For example, perhaps your database contains students from the states of
DE, NJ, and PA and you only want to see the students from DE.
You can filter your data so only DE students display.
Each time you apply a filter to a column, it replaces any previous filter
you applied to that column.
For example, if you apply a filter so you only see students in DE, and
later you apply a filter so you only see students in NJ, Access clears the DE
filter and then applies the NJ filter.
You can apply filters to multiple columns in the same table. For
example, by applying a filterfirst to the State field and then to the Last Name
field, you can see all of the students in the state of DE whose last names are
Adams.
To apply a filter:
1. Click the column label for the column you want to filter.
2. Activate the Home tab.
3. Click the Filter button. A menu appears.
4. Uncheck the items you do not want to appear, making sure only the items
you want are checked.

7. 5. Click OK. Access filters your data and displays the word Filtered at the
bottom of the window.
To remove a filter:
1. Activate the Home tab.
2. Click Advanced in the Sort & Filter group. A menu appears.
3. Click Clear All Filters. Access clears all the filters you have applied.
Creating the 'Relationships' between the tables:
A 'Relationship' is a link that is created and maintained between two tables
that enable data to be accessed from both the tables simultaneously.
Once the tables have been created, there is need to specify the
relationship that exists between the tables.
This will come in handy when the user wants to retrieve information
that exists in more than one table, as one unit.
Although this can be done even at a later stage, it is appropriate that we
define the relationships when the tables are initially being created.
To create relationships:
i. Close all tables and forms. (Right-click on the tab of any Object. A
menu appears. Click Close All.)
ii. Activate the Database Tools tab.
iii. Click the Relationships button in the Show/Hide group. The
Relationships window appears.
iv. Click the Show Table button in the Relationships group. The Show
Table dialog box appears.
v. Activate the Tables tab if your relationships will be based on tables,
activate the queries tab if your relationships will be based on queries, or
activate the both tab if your relationships will bebased on both.
vi. Double-click each table or query you want to use to build a relationship.
The tables appear inthe Relationships window.
vii. Click the Close button to close the Show Table dialog box.
viii. Drag the Primary table’s primary key over the related table’s foreign
key. After you drag theprimary key to the related table’s box, the cursor
changes to an arrow. Make sure the arrowpoints to the foreign key. The
Edit Relationships Dialog box appears.
ix. Click the Enforce Referential Integrity checkbox.
x. Click Create. Access creates a one-to-many relationship between the
tables.
xi. Click the Save button on the Quick Access toolbar to save the
relationship.

8. Tip: When you create a relationship, you can view the related table as a subdatasheetof the primary table. Open the primary table and click the plus (+) in
the far left column. Theplus sign turns into a minus (-) sign. If the Insert
Subdatasheet dialog box opens, click the tableyou want to view as a subdatasheet and then click OK. Access displays the sub-datasheet eachtime you
click the plus sign in the far left column. Click the minus sign to hide thesubdatasheet.
Queries
You use queries to retrieve specific data from your database and to
answer questions about your data. For example, you can use a query to find
the names of the employees in your database who live in a particular state.
Creating Microsoft Access Queries
A query can be based on tables or on other queries. To create a query, you
open the tables or queries on which you are going to base your query in
Query Design view, and then use the options in Design view to create your
query. You then click the Run button to display theresults. You can save
queries for later use.
To open tables or queries in Query Design view:
1. Activate the Create tab.
2. Click the Query Design button in the other group. The Show Table
dialog box appears.
3. Activate the Tables tab if you want to base your query on tables,
activate the Queries tab if you want base your query on queries or
activate the both tab if you want to base your query on bothtables and
queries.
4. Click to choose the table or query on which you want to base your
query.
5. Click Add. The table appears in the window.
a. Click to choose the next table or query on which you want to base
your query.
b. Continue clicking tables or queries until you have all the tables
and queries you plan to use.
6. Click Close. Access changes to Query Design view.
Display All Records and All Fields

9. In Query Design view, each table has an option that allows you to display all
of the fields and allof the records in a table. This option appears on the field
line on the drop-down menu as thetable name followed by a period and an
asterisk (tablename.*).
To display all records and all fields:
1. Open a table or query in Query Design view.
2. Click the down-arrow in the first field on the Field row and then select
the tablename.* option.The table name appears on the table line.
3. Click the Run button. Access retrieves all of the fields and records for
the table and displaysthem in Datasheet view.
Change from Datasheet View to Query Design View
After you run a query, you can easily change back to Query Design view and
make modificationsto your query or create a new query.
To change to Query Design view:
1. Activate the Home tab.
2. Click the down-arrow below View in the Views group. A menu appears.
3. Click Design View. Access changes to Query Design view. You can
modify your query.
Retrieve a Single Column
You can use an Access query to retrieve a single column of data. Instead of
choosing thetablename.* option on the Field line in Query Design view,
choose the name of the field youwant to retrieve.
To retrieve a single column:
1. Open a table or query in Query Design view.
2. Choose the field name you want to display in the field line.
3. Click the Run button. Access retrieves the column you chose.
Retrieve Multiple Columns
You can use an Access query to retrieve multiple columns of data. On the
Field line in QueryDesign view, choose the field name of each field you want
to retrieve in the order you want toretrieve them.
To retrieve multiple columns:
1. Open a table or query in Query Design view.
2. Choose the field names you want to retrieve in the order you want to
retrieve them.

10. 3. Click the Run button. Access retrieves the columns you choose.
Forms
Forms give you the ability to choose the format and arrangement of
fields. You can use a form to enter, edit, and display data.
Reports
Reports organize or summarize your data so you can print it or view it
on screen. You often use reports when you want to analyze your data or
present your data to others.