SAP 7090310 Datový list stáhnout pdf (Strana 508)

100

101

request. If not, it goes to the second order number, and checks that customer name. When an order

number is reached that contains the correct customer name, the database engine retrieves the

information, then continues to the next order number. Using this technique, both the Order# field and

the Customer field must be read for every single record in the table. This takes a long time and a large

amount of computer processing effort for examining extensive database tables with thousands, or even

millions of records.

Instead, you can create an index for the table based on the Customer field. Such an index might look

like this:

Pointer to Order#Customer

10444Allez Distribution

10470BG Mountain Inc.

10511BG Mountain Inc.

10501La Bomba de Bicicleta

10488Mountain Toad

10568Mountain Tops Inc.

10495SFB Inc.

10544Sierra Bicycle Group

10579Sierra Bicycle Group

10485Sierra Mountain

In this index, information is organized by customers, not order numbers. Also, notice that the second

column actually contains pointers to specific order numbers in the original table. By using this index,

the database engine can search just the information in the Customer column until it finds the customer

you are interested in, Sierra Bicycle Group.

For each correct customer entry the database engine finds in the index, it looks up the matching order

in the table according to the pointer in the second column of the index. Only the orders for the correct

customer are read. Finally, since information in the index is organized according to the customer names,

2011-05-16508

Understanding Databases

1 2 ... 503 504 505 506 507 508 509 510 511 512 513 ... 705 706

Komentáře k této Příručce

Vikixwk 04 Jan 2024 | 13:20:14

urenrjrjkvnm

Viktorihon 14 Jan 2024 | 00:44:53

Cinema

SAP 7090310 Datový list Strana 508

Komentáře k této Příručce