Syntax:
SHOW WARNINGS [LIMIT [offset,] row_count]
SHOW COUNT(*) WARNINGS

SHOW WARNINGS is a diagnostic statement that displays information about
the conditions (errors, warnings, and notes) resulting from executing a
statement in the current session. Warnings are generated for DML
statements such as INSERT, UPDATE, and LOAD DATA as well as DDL
statements such as CREATE TABLE and ALTER TABLE.

The LIMIT clause has the same syntax as for the SELECT statement. See
https://dev.mysql.com/doc/refman/5.7/en/select.html.

SHOW WARNINGS is also used following EXPLAIN, to display the extended
information generated by EXPLAIN. See
https://dev.mysql.com/doc/refman/5.7/en/explain-extended.html.

SHOW WARNINGS displays information about the conditions resulting from
execution of the most recent nondiagnostic statement in the current
session. If the most recent statement resulted in an error during
parsing, SHOW WARNINGS shows the resulting conditions, regardless of
statement type (diagnostic or nondiagnostic).

The SHOW COUNT(*) WARNINGS diagnostic statement displays the total
number of errors, warnings, and notes. You can also retrieve this
number from the warning_count system variable:

SHOW COUNT(*) WARNINGS;
SELECT @@warning_count;

A difference in these statements is that the first is a diagnostic
statement that does not clear the message list. The second, because it
is a SELECT statement is considered nondiagnostic and does clear the
message list.

A related diagnostic statement, SHOW ERRORS, shows only error
conditions (it excludes warnings and notes), and SHOW COUNT(*) ERRORS
statement displays the total number of errors. See [HELP SHOW ERRORS].
GET DIAGNOSTICS can be used to examine information for individual
conditions. See [HELP GET DIAGNOSTICS].

URL: https://dev.mysql.com/doc/refman/5.7/en/show-warnings.html

