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Developer on focus
Anton Zamov is a dipl. engineer with more than 6 years of active professional
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MySQL: Can the order of the columns in a create statement make a difference?
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Can the order of the columns in a create statement make a difference? YES
create table t (
a int,
b int,
timeUpdate timestamp,
timeEnter timestamp );
The first timestamp will always be the "automatically generated" time. So
if the record is updated, or inserted, this time gets changed. If the
order is changed, "timeEnter" is before "timeUpdate", then, "timeEnter"
would get updated. First timestamp column updates automatically.
Note, in the table above timeEnter will only get updated if passed a null
value.
insert into t (a,b,timeEnter) values (1,2,NULL);
Hints: Need mm-dd-yyyy hh:mm:ss format?
select a,b,DATE_FORMAT(timeUpdate,'%m-%d-%Y %T'),DATE_FORMAT(timeEnter,'%m-%d-%Y %T') from t;
+------+------+---------------------------------------+--------------------------------------+
| a | b | DATE_FORMAT(timeUpdate,'%m-%d-%Y %T') | DATE_FORMAT(timeEnter,'%m-%d-%Y %T') |
+------+------+---------------------------------------+--------------------------------------+
| 3 | 2 | 04-15-2004 19:14:36 | 04-15-2004 19:15:07 |
| 3 | 2 | 04-15-2004 19:14:39 | 04-15-2004 19:15:07 |
| 5 | 5 | 00-00-0000 00:00:00 | 04-15-2004 19:15:53 |
| 1 | 2 | 00-00-0000 00:00:00 | 04-15-2004 19:20:15 |
+------+------+---------------------------------------+--------------------------------------+
4 rows in set (0.00 sec)
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About the author of this programming example or tutorial:
Mike Chirico (mchirico@users.sourceforge.net)
Copyright (c) 2004 (GPU Free Documentation License)
Last Updated: Tue Jul 20 12:14:51 EDT 2004
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