Rechercher dans le manuel MySQL
13.7.6.40 SHOW WARNINGS Syntax
SHOW WARNINGS
is a diagnostic
statement that displays information about the conditions
(errors, warnings, and notes) resulting from executing a
statement in the current session. Warnings are generated for DML
statements such as INSERT
,
UPDATE
, and
LOAD DATA
INFILE
as well as DDL statements such as
CREATE TABLE
and
ALTER TABLE
.
The LIMIT
clause has the same syntax as for
the SELECT
statement. See
Section 13.2.10, “SELECT Syntax”.
SHOW WARNINGS
is also used
following EXPLAIN
, to display the
extended information generated by
EXPLAIN
. See
Section 8.8.3, “Extended EXPLAIN Output Format”.
SHOW WARNINGS
displays
information about the conditions resulting from execution of the
most recent nondiagnostic statement in the current session. If
the most recent statement resulted in an error during parsing,
SHOW WARNINGS
shows the resulting
conditions, regardless of statement type (diagnostic or
nondiagnostic).
The SHOW COUNT(*)
WARNINGS
diagnostic statement displays the total
number of errors, warnings, and notes. You can also retrieve
this number from the
warning_count
system variable:
A difference in these statements is that the first is a
diagnostic statement that does not clear the message list. The
second, because it is a SELECT
statement is considered nondiagnostic and does clear the message
list.
A related diagnostic statement, SHOW
ERRORS
, shows only error conditions (it excludes
warnings and notes), and
SHOW COUNT(*)
ERRORS
statement displays the total number of errors.
See Section 13.7.6.17, “SHOW ERRORS Syntax”. GET
DIAGNOSTICS
can be used to examine information for
individual conditions. See Section 13.6.7.3, “GET DIAGNOSTICS Syntax”.
Here is a simple example that shows data-conversion warnings for
INSERT
. The example assumes that
strict SQL mode is disabled. With strict mode enabled, the
warnings would become errors and terminate the
INSERT
.
- Query OK, 0 rows affected (0.05 sec)
- *************************** 1. row ***************************
- Level: Warning
- Code: 1265
- *************************** 2. row ***************************
- Level: Warning
- Code: 1048
- *************************** 3. row ***************************
- Level: Warning
- Code: 1264
The max_error_count
system
variable controls the maximum number of error, warning, and note
messages for which the server stores information, and thus the
number of messages that SHOW
WARNINGS
displays. To change the number of messages
the server can store, change the value of
max_error_count
.
max_error_count
controls only
how many messages are stored, not how many are counted. The
value of warning_count
is not
limited by max_error_count
,
even if the number of messages generated exceeds
max_error_count
. The following
example demonstrates this. The ALTER
TABLE
statement produces three warning messages
(strict SQL mode is disabled for the example to prevent an error
from occuring after a single conversion issue). Only one message
is stored and displayed because
max_error_count
has been set to
1, but all three are counted (as shown by the value of
warning_count
):
- +-----------------+-------+
- +-----------------+-------+
- | max_error_count | 1024 |
- +-----------------+-------+
- Query OK, 0 rows affected (0.00 sec)
- +---------+------+----------------------------------------+
- | Level | Code | Message |
- +---------+------+----------------------------------------+
- +---------+------+----------------------------------------+
- +-----------------+
- | @@warning_count |
- +-----------------+
- | 3 |
- +-----------------+
To disable message storage, set
max_error_count
to 0. In this
case, warning_count
still
indicates how many warnings occurred, but messages are not
stored and cannot be displayed.
The sql_notes
system variable
controls whether note messages increment
warning_count
and whether the
server stores them. By default,
sql_notes
is 1, but if set to
0, notes do not increment
warning_count
and the server
does not store them:
- Query OK, 0 rows affected, 1 warning (0.00 sec)
- +-------+------+------------------------------------+
- | Level | Code | Message |
- +-------+------+------------------------------------+
- +-------+------+------------------------------------+
- Query OK, 0 rows affected (0.00 sec)
The MySQL server sends to each client a count indicating the
total number of errors, warnings, and notes resulting from the
most recent statement executed by that client. From the C API,
this value can be obtained by calling
mysql_warning_count()
. See
Section 28.7.7.82, “mysql_warning_count()”.
In the mysql client, you can enable and
disable automatic warnings display using the
warnings
and nowarning
commands, respectively, or their shortcuts,
\W
and \w
(see
Section 4.5.1.2, “mysql Commands”). For example:
Traduction non disponible
Le manuel MySQL n'est pas encore traduit en français sur l'infobrol. Seule la version anglaise est disponible pour l'instant.
Document créé le 26/06/2006, dernière modification le 26/10/2018
Source du document imprimé : https://www.gaudry.be/mysql-rf-show-warnings.html
L'infobrol est un site personnel dont le contenu n'engage que moi. Le texte est mis à disposition sous licence CreativeCommons(BY-NC-SA). Plus d'info sur les conditions d'utilisation et sur l'auteur.
Références
Ces références et liens indiquent des documents consultés lors de la rédaction de cette page, ou qui peuvent apporter un complément d'information, mais les auteurs de ces sources ne peuvent être tenus responsables du contenu de cette page.
L'auteur de ce site est seul responsable de la manière dont sont présentés ici les différents concepts, et des libertés qui sont prises avec les ouvrages de référence. N'oubliez pas que vous devez croiser les informations de sources multiples afin de diminuer les risques d'erreurs.