How can you lock record using SOQL in Salesforce so that it cannot be modified by other user?

Hi Saurabh,

In Apex, you can use FOR UPDATE to lock sObject records while they’re being updated in order to prevent race conditions and other thread safety problems.
While an sObject record is locked, no other client or user is allowed to make updates either through code or the Salesforce user interface.

For example, the following statement, in addition to querying for two accounts, also locks the accounts that are returned:

Account [] accts = [SELECT Id FROM Account LIMIT 2 FOR UPDATE];