Hash Algorithm

[Former Member]

Hi Experts,

Pls explain Hash Algorithm with one example

Thanks In Advance,

Ur's

Harsha.

[sukhbold_altanbat]

Hi Harsha,

check these out (general information):

<a href="http://en.wikipedia.org/wiki/Hash_function">Hash function</a>

<a href="http://en.wikipedia.org/wiki/Hash_table">Hash table</a>

<a href="http://en.wikipedia.org/wiki/Hash_list">Hash list</a>

<a href="http://en.wikipedia.org/wiki/Hash_tree">Hash tree</a>

Regards,

Sukhee

[VijayaDeepthi]

these links are not opened it's showing Error.

[Former Member]

if you want a internal table which allows faster reading then you should go for hashed table , but the disadvantage is that you cannot use index to read the hashed itab.

you have to use keys.

sample declratin of hashed table.

data:cc_text TYPE HASHED TABLE OF /bi0/tcostcenter WITH UNIQUE KEY co_area costcenter langu .

to read entries from the hashed table.

READ TABLE cc_text INTO wa_cc_text WITH KEY

co_area = coarea

costcenter = cctr

langu = sy-langu .

Hash table access time dosent increase based on the number of records, its constant.

check out the ABAP key work documentation for different types of internal table and their usages.

> How Hash Algorithm and Logarithmic Algorithm works

> to fetch the data ?

Fetching part is the same as standard internal table, only when you work with the internal table, than it's different.

> What the basic things we have to keep in mined when

> we select the Internal table ?

Eg Performance.

> Any rule for selecting the internal table which

> should be followed ?

Standard table is quite easy to use, but you might loose performance with it. Most of the time hash table is the fastest.

Using standard table and sort it is a good choice, when you access in READ TABLE via BINARY SEARCH.

Check 'ABAP for Power Users' SAP tutorial in SDN, it very good explains this topic in detail.

http://www.sap.info/public/en/category.php4/Category-28943c61b1e60d84b/page/0/article/Article-119884...

Regards,

Pavan