The CALL statement invokes a stored procedure that was defined
previously with CREATE PROCEDURE.
Stored procedures that take no arguments can be invoked without
parentheses. That is, CALL p() and CALL p are equivalent.
CALL can pass back values to its caller using parameters that are
declared as OUT or INOUT parameters. When the procedure returns, a
client program can also obtain the number of rows affected for the
final statement executed within the routine: At the SQL level, call the
ROW_COUNT() function; from the C API, call the mysql_affected_rows()
For information about the effect of unhandled conditions on procedure