检查慢查日志是否开启：
show variables like 'slow_query_log'
show variables like 'slow_query_log'
//查看是否开启慢查询日志
set global slow_query_log_file=' /usr/share/mysql/sql_log/mysql-slow.log'
//慢查询日志的位置
set global log_queries_not_using_indexes=on;
//开启慢查询日志
set global long_query_time=1;
//大于1秒钟的数据记录到慢日志中，如果设置为默认0，则会有大量的信息存储在磁盘中，磁盘很容易满掉
查看所有日志的变量信息
show variables like '%log%'
mysql> show variables like '%log%';
+-----------------------------------------+------------------------------------+
| Variable_name | Value |
+-----------------------------------------+------------------------------------+
| back_log | 80 |
| binlog_cache_size | 32768 |
| binlog_checksum | CRC32 |
| binlog_direct_non_transactional_updates | OFF |
| binlog_error_action | IGNORE_ERROR |
| binlog_format | STATEMENT |
| binlog_gtid_simple_recovery | OFF |
| binlog_max_flush_queue_time | 0 |
| binlog_order_commits | ON |
| binlog_row_image | FULL |
| binlog_rows_query_log_events | OFF |
| binlog_stmt_cache_size | 32768 |
| binlogging_impossible_mode | IGNORE_ERROR |
| expire_logs_days | 0 |
| general_log | OFF |
| general_log_file | /var/lib/mysql/mysql-host.log |
| innodb_api_enable_binlog | OFF |
| innodb_flush_log_at_timeout | 1 |
| innodb_flush_log_at_trx_commit | 1 |
| innodb_locks_unsafe_for_binlog | OFF |
| innodb_log_buffer_size | 8388608 |
| innodb_log_compressed_pages | ON |
| innodb_log_file_size | 50331648 |
| innodb_log_files_in_group | 2 |
| innodb_log_group_home_dir | ./ |
| innodb_mirrored_log_groups | 1 |
| innodb_online_alter_log_max_size | 134217728 |
| innodb_undo_logs | 128 |
| log_bin | OFF |
| log_bin_basename | |
| log_bin_index | |
| log_bin_trust_function_creators | OFF |
| log_bin_use_v1_row_events | OFF |
| log_error | /var/log/mysqld.log |
| log_output | FILE |
| log_queries_not_using_indexes | ON |
| log_slave_updates | OFF |
| log_slow_admin_statements | OFF |
| log_slow_slave_statements | OFF |
| log_throttle_queries_not_using_indexes | 0 |
| log_warnings | 1 |
| max_binlog_cache_size | 18446744073709547520 |
| max_binlog_size | 1073741824 |
| max_binlog_stmt_cache_size | 18446744073709547520 |
| max_relay_log_size | 0 |
| relay_log | |
| relay_log_basename | |
| relay_log_index | |
| relay_log_info_file | relay-log.info |
| relay_log_info_repository | FILE |
| relay_log_purge | ON |
| relay_log_recovery | OFF |
| relay_log_space_limit | 0 |
| simplified_binlog_gtid_recovery | OFF |
| slow_query_log | OFF |
| slow_query_log_file | /var/lib/mysql/mysql-host-slow.log |
| sql_log_bin | ON |
| sql_log_off | OFF |
| sync_binlog | 0 |
| sync_relay_log | 10000 |
| sync_relay_log_info | 10000 |
+-----------------------------------------+-----------------------------------
开启慢查日志：
show variables like 'slow_query_log'
//查看是否开启慢查询日志
set global slow_query_log_file=' /var/lib/mysql/mysql-host-slow.log '
//慢查询日志的位置
set global log_queries_not_using_indexes=on;
//开启慢查询日志
set global long_query_time=1;
//大于1秒钟的数据记录到慢日志中，如果设置为默认0，则会有大量的信息存储在磁盘中，磁盘很容易满掉
验证慢查询日志是否开启：
在mysql操作中，
Show databases;
Use sakila;
select * from store;
select * from staff;
监听日志文件，看是否写入
tail -50f /var/lib/mysql/mysql-host-slow.log