SHOW WARNINGS [LIMIT [offset,] row_count] SHOW ERRORS [LIMIT row_count OFFSET offset] SHOW COUNT(*) WARNINGS
SHOW WARNINGS
shows the error, warning, and note messages that resulted from the last statement that generated messages in the current session. It shows nothing if the last statement used a table and generated no messages. (That is, a statement that uses a table but generates no messages clears the message list.) Statements that do not use tables and do not generate messages have no effect on the message list.
A note is different to a warning in that it only appears if the sql_notes
variable is set to 1 (the default), and is not converted to an error if strict mode
is enabled.
A related statement, SHOW ERRORS
, shows only the errors.
The SHOW COUNT(*) WARNINGS
statement displays the total number of errors, warnings, and notes. You can also retrieve this number from the warning_count variable:
SHOW COUNT(*) WARNINGS; SELECT @@warning_count;
The value of warning_count
might be greater than the number of messages displayed by SHOW WARNINGS
if the max_error_count
system variable is set so low that not all messages are stored.
The LIMIT
clause has the same syntax as for the SELECT statement
.
SHOW WARNINGS
can be used after EXPLAIN EXTENDED
to see how a query is internally rewritten by MariaDB.
If the sql_notes
server variable is set to 1, Notes are included in the output of SHOW WARNINGS
; if it is set to 0, this statement will not show (or count) Notes.
The results of SHOW WARNINGS
and SHOW COUNT(*) WARNINGS
are directly sent to the client. If you need to access those information in a stored program, you can use the GET DIAGNOSTICS
statement instead.
For a list of MariaDB error codes, see MariaDB Error Codes.
The mysql
client also has a number of options related to warnings. The \W
command will show warnings after every statement, while \w
will disable this. Starting the client with the --show-warnings
option will show warnings after every statement.
MariaDB 10.3.1 implements a stored routine error stack trace. SHOW WARNINGS
can also be used to show more information. See the example below.
SELECT 1/0; +------+ | 1/0 | +------+ | NULL | +------+ SHOW COUNT(*) WARNINGS; +-------------------------+ | @@session.warning_count | +-------------------------+ | 1 | +-------------------------+ SHOW WARNINGS; +---------+------+---------------+ | Level | Code | Message | +---------+------+---------------+ | Warning | 1365 | Division by 0 | +---------+------+---------------+
From MariaDB 10.3.1, displaying a stack trace:
DELIMITER $$ CREATE OR REPLACE PROCEDURE p1() BEGIN DECLARE c CURSOR FOR SELECT * FROM not_existing; OPEN c; CLOSE c; END; $$ CREATE OR REPLACE PROCEDURE p2() BEGIN CALL p1; END; $$ DELIMITER ; CALL p2; ERROR 1146 (42S02): Table 'test.not_existing' doesn't exist SHOW WARNINGS; +-------+------+-----------------------------------------+ | Level | Code | Message | +-------+------+-----------------------------------------+ | Error | 1146 | Table 'test.not_existing' doesn't exist | | Note | 4091 | At line 6 in test.p1 | | Note | 4091 | At line 4 in test.p2 | +-------+------+-----------------------------------------+
SHOW WARNINGS
displays a stack trace, showing where the error actually happened:
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Licensed under the Creative Commons Attribution 3.0 Unported License and the GNU Free Documentation License.
https://mariadb.com/kb/en/show-warnings/