How to achieve when I update the account field by name billing street then the same field which contains in contact need to be updated by a Trigger written on Account object?
Go through the following cook book article which has sample code and explaination which you can test on your ORG: http://developer.force.com/cookbook/recipe/mass-updating-contacts-when-an-account-changes
If I understood your requirement correctly, you want that the Billing Street on all contacts should be updated once the Account Billing Street changes. To do this, you will need a trigger and a workflow. a. Create a trigger on Account, that only runs if the Billing Street changes, and blindly updates all contacts - this will run the workflow rule that you will create in the next step. b. Create a workflow rule on Contact, that updates the Contact's Billing Street with that of the Account.
Go through the following cook book article which has sample code and explaination which you can test on your ORG: http://developer.force.com/cookbook/recipe/mass-updating-contacts-when-an-account-changes
http://developer.force.com/cookbook/recipe/mass-updating-contacts-when-an-account-changes
All Answers
If I understood your requirement correctly, you want that the Billing Street on all contacts should be updated once the Account Billing Street changes.
To do this, you will need a trigger and a workflow.
a. Create a trigger on Account, that only runs if the Billing Street changes, and blindly updates all contacts - this will run the workflow rule that you will create in the next step.
b. Create a workflow rule on Contact, that updates the Contact's Billing Street with that of the Account.
This should do it! Cheers!
http://developer.force.com/cookbook/recipe/mass-updating-contacts-when-an-account-changes