Hi
AFAIK, before changing data, the old values are saved in the rollback
segment.
On saving the updated values, from the Buffer to the rollback segment/data
files,
--- it checks if there is any matched row that matches the condition. If
found, then flags "Matched".
---after filtering out the matched row, it check whether there is need to
change the old value to new value. if need then flags "Changed" and rewrite
the same in the datafile/rollback segment.
Thanks
ViSolve DB Team.
----- Original Message -----
From: "Ace" <[EMAIL PROTECTED]>
To: <mysql@lists.mysql.com>
Sent: Monday, June 11, 2007 11:41 AM
Subject: how to get Number of rows matched?
Hi Experts,
When issuing updates in mysql (in the console window), mysql will tell
you if any rows matched and how many rows were updated (see below). I
know how to get number of rows udpated using mysql_affected_rows(), but is
there any
way to get the number of rows matched? I want to find out, when rows
updated = 0, if there were no updates because the row wasn't found
(rows matched will = 0) or because the update would not have changed
any data (rows matched = 1).
mysql> select * from test;
+------+------+
| roll | s |
+------+------+
| 1 | new |
+------+------+
1 row in set (0.00 sec)
mysql> update test set roll = 1, s = 'new' where roll = 1;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1 Changed: 0 Warnings: 0
mysql> update test set roll = 1, s = 'new' where roll = 17;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 0 Changed: 0 Warnings: 0
mysql> update test set roll = 1, s = 'neww' where roll = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
--
Cheers,
Rajan
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