Solved

PL/SQL Update Command

Posted on 2006-10-19
4
3,334 Views
Last Modified: 2008-05-18
Question,
         I need to update 1 field in 844 records changing the field from a 3 to a 1, my question is this, I am new to plsql and need to know what the safest way of updating records in oracle is, is it best to use a selection statement followed by an update statement or just an update statement with the (where in)  statement with the record identifiers.

what i really need is a way of being able to test the data selection before i update to make sure it will update only the records i want and to be able to run the update knowing what it is going to get updated is only what was selected above and not all records.


Thanks.


0
Comment
Question by:eenderle
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
4 Comments
 
LVL 35

Assisted Solution

by:Raynard7
Raynard7 earned 250 total points
ID: 17770107
Hi,

An update with a where in should be safest,

If you are using a transaction based table then you could run the update - check your data and if satisfied then commit your transaction, alternativley you could roll it back.

Or you could make a copy of your table into a temporary table and run the update there.  This is personal preference.
0
 
LVL 27

Expert Comment

by:sujith80
ID: 17771583
If you are using the same where clause for selecting the data and updating then no need to worry about it.
from a pl/sql block you can print the number of records updated like below.

set serveroutput on
begin
<your update statement>;
dbms_output.put_line(SQL%rowcount);
end;
/

So, you can run the select statement before the update and match the count with the value printed from the above block.
0
 
LVL 6

Accepted Solution

by:
makhan earned 250 total points
ID: 17772457
Hi,

First do a select statement with a where condition i.e.

select col1, col2
  from tab1
 where colx between 1 and 100

this will return <n> rows.

next use the update.

update tab1
     set col1 = <value>
 where colx between 1 and 100

this will update <n> rows

compare <n> in the first step with <n> in the second step.

these two should be equal.

Regards,

makhan

0
 
LVL 22

Expert Comment

by:earth man2
ID: 17772694
You may want to lock the rows before you update them if you have to worry bout multiuser issues.
ie select .. for update;
update;
commit;
0

Featured Post

Free Tool: ZipGrep

ZipGrep is a utility that can list and search zip (.war, .ear, .jar, etc) archives for text patterns, without the need to extract the archive's contents.

One of a set of tools we're offering as a way to say thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Configuring and using Oracle Database Gateway for ODBC Introduction First, a brief summary of what a Database Gateway is.  A Gateway is a set of driver agents and configurations that allow an Oracle database to communicate with other platforms…
Using SQL Scripts we can save all the SQL queries as files that we use very frequently on our database later point of time. This is one of the feature present under SQL Workshop in Oracle Application Express.
This video shows information on the Oracle Data Dictionary, starting with the Oracle documentation, explaining the different types of Data Dictionary views available by group and permissions as well as giving examples on how to retrieve data from th…
This video explains what a user managed backup is and shows how to take one, providing a couple of simple example scripts.

739 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question