basic SQL atomicity "UPDATE ... SET .. WHERE ..."
- by elgcom
I have a rather basic and general question about atomicity of "UPDATE ... SET .. WHERE ..." statement.
having a table (without extra constraint),
+----------+
| id | name|
+----------+
| 1 | a |
+----+-----+
now, I would execute following 4 statements "at the same time" (concurrently).
UPDATE table SET name='b1' WHERE name='a'
UPDATE table SET name='b2' WHERE name='a'
UPDATE table SET name='b3' WHERE name='a'
UPDATE table SET name='b4' WHERE name='a'
is there only one UPDATE statement would be executed with table update?
or, is it possible that more than one UPDATE statements can really update the table?
should I need extra transaction or lock to let only one UPDATE write values into table?
thanks
