Transcript Working with Derby

Working with Derby
Creating tables
• We know how to create a database in
Derby – an empty database
• Next step is to add tables to the database
• After adding tables, we can enter data into
the tables
• Remember; design your tables BEFORE
using Derby to enter them 
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Creating tables
Before using a
database, we
must connect to it
Right-click on
database, and
choose ”Connect”
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Creating tables
Enter whatever we
chose when creating the database
(hopefully just
blanks…)
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Creating tables
Now we can access
the tables in the
database – but there
are none yet
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Creating tables
Right-click on ”Tables”,
and choose ”Create
table”
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Creating tables
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Creating tables
• Recall what we need in order to define a
table
– A proper name for the table
– A set of field definitions – a name and a type
for each field
– A key field – one or more fields the
combination of which is always unique
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Creating tables
Enter a proper name
for the table
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Creating tables
• For each data field (also called column),
we must add quite a lot of information:
– Column name: Name of the data field
– Key: Is the field part of the key field
– Index: Leave as-is…
– Null: Can we omit the value
– Unique: Must the value be unique
– Data type: Proper type of data
– Size: How large can the data be
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Creating tables
• Example: a Name field
– Column name: Name
– Key: Yes
– Null: No
– Unique: (decided by choosing ”Key”)
– Data type: VARCHAR (means ”String”)
– Size: 50 (how long can a name be…?)
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Creating tables
• Example: a Phone field
– Column name: Phone
– Key: Yes
– Null: No
– Unique: (decided by choosing ”Key”)
– Data type: NUMERIC (number)
– Size: 8 (a Danish phone number)
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Creating tables
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Creating tables
A database called
Phone Book
A table called
Friend
Red indicates
that field is part
of key field
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Two data fields:
Name, Phone
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Creating tables
We can add more
data fields later
Right-click on the
table, choose ”Add
Column…”
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Creating tables
Same as before, but
different dialog…
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Creating tables
Exercise
– Create a database called WebShop in Derby
– Create three tables in WebShop, called Item, Customer, Sale
– Definitions of the tables are given below (key fields are in red)
Item
ItemNumber
ItemName
Price
Weight
NumberInStock
IsFragile
Description
Customer
CustomerNumber
Name
Address
ZipCode
E-mail
ClubMember
LastSale
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Sale
CustomerNumber
ItemNumber
Date
NumberOfItems
TotalAmount
SentToCustomer
PaymentReceived
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Adding data
With the table definition in place, we can
now begin to add
data to the table
Right-click on the
table, choose ”View
Data…”
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Adding data
Data in the table is
shown here (none
yet….)
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Adding data
Press this
icon to add
new data
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Adding data
Type in data for
this particular
record
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Adding data
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Adding data
Table now contains one record
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Adding data
And so on,
and so on…
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Adding data
• What can go wrong…?
• We might try to type in
some data, that does
not match the type
specification for a
particular field
• Derby will complain…
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Adding data
What is wrong
here…?
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Adding data
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Adding data
• The error messages can be more or less
easy to understand…
• It is almost always a matter of trying to
enter data of the wrong type
• Might also be data of incorrect size
• Some errors are more subtle, like a wrong
date (30-02-1988)
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Adding data
What is this…?
An SQL query!
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Adding data
Exercise
– Add a few records to the tables created in the earlier exercise.
Try to experiment with the data, such that you also try to add
some data with errors. Observe the errors messages that Derby
returns when data has errors
– Do you now feel comfortable working with Derby, with regards to
creating databases, tables and fields, and entering data into
tables? If not, then try to invent some more tables, enter them
into a database, and enter some data into the tables
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