There are several sources of error information in MySQL:
Each SQL statement executed results in an error code, an SQLSTATE value, and an error message, as described in Section B.2, “Types of Error Values”. These errors are returned from the server side; see Section B.3, “Server Error Codes and Messages”.
Errors can occur on the client side, usually involving problems communicating with the server; see Section B.4, “Client Error Codes and Messages”.
SQL statement warning and error information is available
through the SHOW WARNINGS and
SHOW ERRORS statements. The
warning_count system variable
indicates the number of errors, warnings, and notes. The
error_count system variable
indicates the number of errors. Its value excludes warnings
and notes.
SHOW SLAVE STATUS statement
output includes information about replication errors occurring
on the slave side.
SHOW ENGINE
INNODB STATUS statement output includes information
about the most recent foreign key error if a
CREATE TABLE statement for an
InnoDB table fails.
The perror program provides information from the command line about error numbers. See Section 4.8.1, “perror — Explain Error Codes”.
Descriptions of server and client errors are provided later in
this Appendix. For information about errors related to
InnoDB, see
Section 14.23.4, “InnoDB Error Handling”.