C.1. Sources of Error Information

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 C.2, "Types of Error Values". These errors are returned from the server side; see Section C.3, "Server Error Codes and Messages".
Errors can occur on the client side, usually involving problems communicating with the server; see Section C.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.
The GET DIAGNOSTICS statement may be used to inspect the diagnostic information in the diagnostics area. See Section 13.6.7.3, "GET DIAGNOSTICS Syntax".
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 14.2.3.14, "InnoDB Error Handling".