Query taking 99% CPU usage for only fetching 623 rows

[Maron Vomr@]

Dear all,
I have a database with 300 tables and for some times facing some performance issues regarding the queries.

Whenever users tries to fetch a report which actually finally fetches aroudn 700 rows out of 1 lacs rows gives the CPU to rise 99.9% and stays there for the time of the whole report run.

below are the table structure which is it actually queries for data

CREATE TABLE `request_detail` (
`id` int(11) NOT NULL auto_increment,
`ticket_no` varchar(20) NOT NULL default '',
`re_ticket_no` varchar(20) NOT NULL default '',
`req_date` datetime NOT NULL default '0000-00-00 00:00:00',
`expected_date` datetime NOT NULL default '0000-00-00 00:00:00',
`action_date` datetime NOT NULL default '0000-00-00 00:00:00',
`remarks` text NOT NULL,
`status` varchar(50) NOT NULL default 'Pending',
`reopen_status` tinyint(4) NOT NULL default '0',
`assign_to` varchar(50) NOT NULL default '',
PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=103440 DEFAULT CHARSET=latin1

One more thing what the the AUTO_INCREMENT=103440 means beside ENGINE?

I am using server version: 4.1.22-standard on a 32 bit server.

mysql> show status;
+----------------------------+-------------+
| Variable_name | Value |
+----------------------------+-------------+
| Aborted_clients | 109231 |
| Aborted_connects | 55329 |
| Binlog_cache_disk_use | 0 |
| Binlog_cache_use | 0 |
| Bytes_received | 2758435647 |
| Bytes_sent | 972852577 |
| Com_admin_commands | 3483332 |
| Com_alter_db | 0 |
| Com_alter_table | 1 |
| Com_analyze | 2 |
| Com_backup_table | 0 |
| Com_begin | 0 |
| Com_change_db | 294885517 |
| Com_change_master | 0 |
| Com_check | 1 |
| Com_checksum | 0 |
| Com_commit | 0 |
| Com_create_db | 1 |
| Com_create_function | 0 |
| Com_create_index | 0 |
| Com_create_table | 25 |
| Com_dealloc_sql | 0 |
| Com_delete | 3578184 |
| Com_delete_multi | 0 |
| Com_do | 0 |
| Com_drop_db | 0 |
| Com_drop_function | 0 |
| Com_drop_index | 0 |
| Com_drop_table | 0 |
| Com_drop_user | 0 |
| Com_execute_sql | 0 |
| Com_flush | 5 |
| Com_grant | 0 |
| Com_ha_close | 0 |
| Com_ha_open | 0 |
| Com_ha_read | 0 |
| Com_help | 0 |
| Com_insert | 5250093 |
| Com_insert_select | 3613 |
| Com_kill | 0 |
| Com_load | 0 |
| Com_load_master_data | 0 |
| Com_load_master_table | 0 |
| Com_lock_tables | 379 |
| Com_optimize | 1 |
| Com_preload_keys | 0 |
| Com_prepare_sql | 0 |
| Com_purge | 0 |
| Com_purge_before_date | 0 |
| Com_rename_table | 0 |
| Com_repair | 0 |
| Com_replace | 13436 |
| Com_replace_select | 0 |
| Com_reset | 0 |
| Com_restore_table | 0 |
| Com_revoke | 0 |
| Com_revoke_all | 0 |
| Com_rollback | 0 |
| Com_savepoint | 0 |
| Com_select | 974280849 |
| Com_set_option | 33628 |
| Com_show_binlog_events | 0 |
| Com_show_binlogs | 0 |
| Com_show_charsets | 0 |
| Com_show_collations | 0 |
| Com_show_column_types | 0 |
| Com_show_create_db | 0 |
| Com_show_create_table | 33258 |
| Com_show_databases | 74 |
| Com_show_errors | 0 |
| Com_show_fields | 46731 |
| Com_show_grants | 0 |
| Com_show_innodb_status | 0 |
| Com_show_keys | 0 |
| Com_show_logs | 0 |
| Com_show_master_status | 0 |
| Com_show_ndb_status | 0 |
| Com_show_new_master | 0 |
| Com_show_open_tables | 1 |
| Com_show_privileges | 0 |
| Com_show_processlist | 823 |
| Com_show_slave_hosts | 0 |
| Com_show_slave_status | 0 |
| Com_show_status | 797 |
| Com_show_storage_engines | 0 |
| Com_show_tables | 33782 |
| Com_show_variables | 15 |
| Com_show_warnings | 0 |
| Com_slave_start | 0 |
| Com_slave_stop | 0 |
| Com_stmt_close | 0 |
| Com_stmt_execute | 0 |
| Com_stmt_prepare | 0 |
| Com_stmt_reset | 0 |
| Com_stmt_send_long_data | 0 |
| Com_truncate | 2343 |
| Com_unlock_tables | 379 |
| Com_update | 27277092 |
| Com_update_multi | 2 |
| Connections | 13268855 |
| Created_tmp_disk_tables | 445379 |
| Created_tmp_files | 930 |
| Created_tmp_tables | 2075918 |
| Delayed_errors | 0 |
| Delayed_insert_threads | 0 |
| Delayed_writes | 0 |
| Flush_commands | 1 |
| Handler_commit | 0 |
| Handler_delete | 774470 |
| Handler_discover | 0 |
| Handler_read_first | 31896861 |
| Handler_read_key | 2401490761 |
| Handler_read_next | 2650544974 |
| Handler_read_prev | 3974802986 |
| Handler_read_rnd | 1268129591 |
| Handler_read_rnd_next | 2571601548 |
| Handler_rollback | 0 |
| Handler_update | 48208426 |
| Handler_write | 660600146 |
| Key_blocks_not_flushed | 0 |
| Key_blocks_unused | 3618 |
| Key_blocks_used | 7248 |
| Key_read_requests | 18050355512 |
| Key_reads | 590038314 |
| Key_write_requests | 33805259 |
| Key_writes | 24775788 |
| Max_used_connections | 301 |
| Not_flushed_delayed_rows | 0 |
| Open_files | 120 |
| Open_streams | 0 |
| Open_tables | 64 |
| Opened_tables | 4815669 |
| Qcache_free_blocks | 0 |
| Qcache_free_memory | 0 |
| Qcache_hits | 0 |
| Qcache_inserts | 0 |
| Qcache_lowmem_prunes | 0 |
| Qcache_not_cached | 0 |
| Qcache_queries_in_cache | 0 |
| Qcache_total_blocks | 0 |
| Questions | 1318725562 |
| Rpl_status | NULL |
| Select_full_join | 267371 |
| Select_full_range_join | 0 |
| Select_range | 940972 |
| Select_range_check | 0 |
| Select_scan | 52136070 |
| Slave_open_temp_tables | 0 |
| Slave_retried_transactions | 0 |
| Slave_running | OFF |
| Slow_launch_threads | 1 |
| Slow_queries | 1853 |
| Sort_merge_passes | 463 |
| Sort_range | 290391821 |
| Sort_rows | 1523293431 |
| Sort_scan | 12269146 |
| Table_locks_immediate | 1014600558 |
| Table_locks_waited | 188849 |
| Threads_cached | 0 |
| Threads_connected | 35 |
| Threads_created | 13268854 |
| Threads_running | 2 |

Thanks in advance.