Dear Monks

Lets say you were performing an sql update statement which was supposed to update one row in table A with details from exactly one row from table B because these 2 tables were supposed to have a common field and one row in table A will have the same value for this field as exactly one row in table B. The query would be like this:

The query might be something like

update table A, table B set A.field1 = B.field1 where A.field2 = b.fie
+ld2
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But what would happen if a row in table A actually matched 2 or more rows in table B? Lets say row 5 in table A matched rows 20 and 30 in table B. I am thinking row A will get updated with the value from table B row 20 and then will get updated again with the value from row 30 in table B, this overwriting the previous update

I am trying to simulate this as we speak. But my perl question is what would be the 'number of rows affected' returned by the do method

$rows_affected = $dbh->do($querystr);
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Would it be the number of updates carried out even if the same row in table A was updated multiple times or would it just be one update as only one row in table A is ever updated? many thanks