SELECT FOR UPDATE in CURSORS

SELECT FOR UPDATE in CURSORS - SELECT FOR UPDATE in Cursors...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
SELECT FOR UPDATE in Cursors When you issue a SELECT statement against the database to query some records, no locks are placed on the selected rows. In general, this is a wonderful feature because the number of records locked at any given time is (by default) kept to the absolute minimum: only those records that have been changed but not yet committed are locked. Even then, others will be able to read those records as they appeared before the change (the "before image" of the data). There are times, however, when you will want to lock a set of records even before you change them in your program. Oracle offers the FOR UPDATE clause of the SELECT statement to perform this locking. When you issue a SELECT. ..FOR UPDATE statement, the RDBMS automatically obtains exclusive row-level locks on all the rows identified by the SELECT statement, holding the records "for your changes only" as you move through the rows retrieved by the cursor. No one else will be able to change any of these records until you perform a
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 07/15/2011 for the course ECO 2023 taught by Professor Mr.raza during the Summer '10 term at FAU.

Page1 / 2

SELECT FOR UPDATE in CURSORS - SELECT FOR UPDATE in Cursors...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online