And outstanding invoices

[View full size image]

eld

lasl_name

first .name

shipping address

M

Doe

John

505 Somes) reel

2

Doe

Jane

E05 Êomeslreel

3

Palmer

John

.200 Anyslraa!

4

Jatinson

Richard

1Q0Q Another Sirgel

orders

çid

order ngim

Slock., nu m

priority

shipped

date

<t0DO

100,252,342

3

y

SY31fl)1

1221

200,352

1

N

10/2/01

3

1223

200,121

2

V

1 Cft/01

2

1225

221,152

1

N

order num

days overdue

action

32

sent leller

In the example in Figure 21.3, we have added a customer ID field to each customer record. This field holds a customer ID number that is the unique piece of information that can be used to link all other information for each customer to track orders and invoices. Each customer is given an ID unique to him; two customers might have the same data in their name fields, but their ID field values will never be the same. The Customer ID field data in the Orders and Overdue tables replaces the Last Name, First Name, and Shipping Address field information from the Customers table. Now, when you want to run a search for any customer's order and invoice data, you can search based on one key rather than multiple keys. You get more accurate results in faster, easier-to-conduct data searches.

Now that you have an idea of how data is stored in an RDBMS and how the RDBMS structure enables you to work with that data, you are ready to learn how to input and output data from the database. This is where SQL comes in.

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