SHOW WARNINGS

Display warnings from the last executed statement. View warning codes, messages, and levels for recent operations.

Syntax

SHOW WARNINGS [LIMIT [offset,] row_count]
SHOW ERRORS [LIMIT row_count OFFSET offset]
SHOW COUNT(*) WARNINGS

Description

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.

The mariadb 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 implements a stored routine error stack trace. SHOW WARNINGS can also be used to show more information. See the example below.

Examples

SELECT 1/0;
+------+
| 1/0  |
+------+
| NULL |
+------+

SHOW COUNT(*) WARNINGS;
+-------------------------+
| @@session.warning_count |
+-------------------------+
|                       1 |
+-------------------------+

SHOW WARNINGS;
+---------+------+---------------+
| Level   | Code | Message       |
+---------+------+---------------+
| Warning | 1365 | Division by 0 |
+---------+------+---------------+

Stack Trace

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:

• Line 4 in test.p1 is the OPEN command which actually raised the error.

• Line 3 in test.p2 is the CALL statement, calling p1 from p2.

See Also

• SHOW ERRORS

_{This page is licensed: GPLv2, originally from fill_help_tables.sql}