When is SELECT FOR UPDATE used

Question

DB version:10gR2
Since another thread of mine on this subject didn't go well, i am starting another thread.
When exactly is SELECT..FOR UPDATE statement used? With the exception of using SELECT...FOR UPDATE in CURSOR declaration, I've rarely seen SELECT ...FOR UPDATE being used explicitlyby PL/SQL gurus in our firm. Why didn't they use SELECT..FOR UPDATE(i mean a stand alone SELECT FOR UPDATE, <em>not as a part of Cursor</em>) to lock rows before UPDATE/DELETE/INSERT in their codes?
Edited by: M.Everett on Oct 20, 2008 12:00 PM
edited the initial post to let the users know that I am refering to a stand alone SELECT FOR UPDATE statement, not the part of a cursor

Answer 1

M.Everett wrote:
What i gather from various sources in the Internet:
1. SELECT FOR UPDATE is used mainly on CURSORs and very rarely used as a stand alone statement (if this is not the case you would have seen SELECT FOR UPDATE statements before every UPDATEs and DELETEs in PL/SQL codes)
2. Stand alone SELECT FOR UPDATEs are used mainly when dealing with CLOB, BLOB
Am i right in making these conclusions?1. This is probably a fair assumption.
2. Not really. SELECT FOR UPDATE is not a requirement when dealign with (C|B)LOBs.
SELECT FOR UPDATE allows an easy form of reference when you come to update rows in a cursor loop (although cursor loops should be rarely used), because rather than having to include a where condition on key columns you can just refer to the CURRENT ROW. Obviously, the main reason for using SFUs is the locking and this can become a requirement in some business environments where a user "picks up" a record to deal with and other users will then not see that record in their list or be able to select it for themselves.
;)