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Working with Derby
RHS – 2009 2
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
RHS – 2009 3
Creating tables
Before using a database, we must connect to it
Right-click on database, and choose ”Connect”
RHS – 2009 4
Creating tables
Enter whatever we chose when crea-ting the database(hopefully just blanks…)
RHS – 2009 5
Creating tables
Now we can access the tables in the database – but there are none yet
RHS – 2009 6
Creating tables
Right-click on ”Tables”, and choose ”Create table”
RHS – 2009 7
Creating tables
RHS – 2009 8
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
RHS – 2009 9
Creating tables
Enter a proper name for the table
RHS – 2009 10
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
RHS – 2009 11
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…?)
RHS – 2009 12
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)
RHS – 2009 13
Creating tables
RHS – 2009 14
Creating tables
A database called Phone Book
A table called Friend
Two data fields: Name, PhoneRed indicates
that field is part of key field
RHS – 2009 15
Creating tables
We can add more data fields later
Right-click on the table, choose ”Add Column…”
RHS – 2009 16
Creating tables
Same as before, but different dialog…
RHS – 2009 17
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
Sale CustomerNumber ItemNumber Date NumberOfItems TotalAmount SentToCustomer PaymentReceived
RHS – 2009 18
Adding data
With the table defini-tion in place, we can now begin to add data to the table
Right-click on the table, choose ”View Data…”
RHS – 2009 19
Adding data
Data in the table is shown here (none yet….)
RHS – 2009 20
Adding data
Press this icon to add new data
RHS – 2009 21
Adding data
Type in data for this particular record
RHS – 2009 22
Adding data
RHS – 2009 23
Adding data
Table now con-tains one record
RHS – 2009 24
Adding data
And so on, and so on…
RHS – 2009 25
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…
RHS – 2009 26
Adding data
What is wrong here…?
RHS – 2009 27
Adding data
RHS – 2009 28
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)
RHS – 2009 29
Adding data
What is this…?An SQL query!
RHS – 2009 30
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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