SHOW WARNINGS - MySQL

Overview

The SHOW WARNINGS command in MySQL displays any warnings that have occurred during the execution of the previous statement or the most recent command. Warnings are informational messages that indicate potential problems or issues that may not necessarily prevent the statement from executing successfully but should be addressed.

Syntax

SHOW WARNINGS

Options/Flags

This command does not have any options or flags.

Examples

Example 1: Display warnings after executing a query

mysql> SELECT * FROM table_name WHERE column_name = 'invalid_value';
mysql> SHOW WARNINGS;
+---------+------+--------------------------------------------------------------------+
| Level    | Code | Message                                                                |
+---------+------+--------------------------------------------------------------------+
| Warning  | 1292 | Truncated incorrect DOUBLE value: 'invalid_value'                        |
| Warning  | 1265 | Data truncated for column 'column_name' at row 1                                |
+---------+------+--------------------------------------------------------------------+
2 rows in set (0.00 sec)

Example 2: Clear warnings

After displaying warnings once, you can clear them using the FLUSH WARNINGS command:

mysql> FLUSH WARNINGS;
Query OK, 0 rows affected (0.00 sec)
mysql> SHOW WARNINGS;
Empty set (0.00 sec)

Common Issues

  • No warnings displayed: If no warnings have occurred during the execution of the previous statement or command, the SHOW WARNINGS command will return an empty set.
  • Truncated messages: Warning messages may be truncated if they are too long. To view the full message, use the SHOW FULL WARNINGS command.

Integration

The SHOW WARNINGS command can be used in conjunction with other MySQL commands to troubleshoot errors and ensure data integrity. For example, it can be used after executing a data modification statement to check for any potential warnings or issues:

mysql> UPDATE table_name SET column_name = 'new_value' WHERE condition;
mysql> SHOW WARNINGS;
  • SHOW ERRORS: Displays any errors that have occurred during the execution of the previous statement or command.
  • FLUSH WARNINGS: Clears any warnings that have been displayed using the SHOW WARNINGS command.