Search Help of The key fileds In DB Table ????

hello Helping Minds..

I have some doubts Abt SEARCH HELP.

As i know , in a DB field. For each Primary key fields ,Search help Already created.

So whr u will Use Primary field of a table , its search help is populated automatically,

so when we use a Particular Primary key field in a Screen of Modulepool or REPORT -(selection screen ),Its Search Help will be displayed Automatically...

Ex- When BUKRS field from - - T001 table is used in Modulepool Screen, its Search help is populated Automatically, we don need to create any search help for that.

But BUKRS field does nt have any search help associated with it. as i checked in T001 table >select BUKRS filed ->SRCH HLP .....Then Message is --NoSearch Help Associated.....

So whts d Fundaa... Pls Answer In details...

Thnks in advance To D helping Minds