这是mysql系列第1篇。
本文主要内容
- 背景介绍
- 数据库基础知识介绍
- mysql的安装
- mysql常用的一些命令介绍
- SQL分类
背景介绍
我们每天都在访问各种网站、APP,如微信、QQ、抖音、今日头条、腾讯新闻等,这些东西上面都存在大量的信息,这些信息都需要有地方存储,存储在哪呢?数据库。
所以如果我们需要开发一个网站、app,数据库我们必须掌握的技术,常用的数据库有mysql、oracle、sqlserver、db2等。
上面介绍的几个数据库,oracle性能排名第一,服务也是相当到位的,但是收费也是非常高的,金融公司对数据库稳定性要求比较高,一般会选择oracle。
mysql是免费的,其他几个目前暂时收费的,mysql在互联网公司使用率也是排名第一,资料也非常完善,社区也非常活跃,所以我们主要学习mysql。
mysql系列我们主要介绍
- mysql的基本使用
- mysql性能优化
- 开发过程中mysql一些优秀的案例介绍
数据库常见的概念
DB:数据库,存储数据的容器。
DBMS:数据库管理系统,又称为数据库软件或数据库产品,用于创建或管理DB。
SQL:结构化查询语言,用于和数据库通信的语言,不是某个数据库软件持有的,而是几乎所有的主流数据库软件通用的语言。中国人之间交流需要说汉语,和美国人之间交流需要说英语,和数据库沟通需要说SQL语言。
数据库存储数据的一些特点
数据存放在表中,然后表存放在数据库中
一个库中可以有多张表,每张表具有唯一的名称(表名)来标识自己
表中有一个或多个列,列又称为“字段”,相当于java中的“属性”
表中每一行数据,相当于java中的“对象”
window中安装mysql
官网下载mysql5.7.25:https://dev.mysql.com/downloads/mysql/5.7.html#downloads
win10安装mysql5.7详细步骤可以看:http://itsoku.com/course/3/211
mysql常用的一些命令
mysql启动2种方式
方式1:
cmd中运行services.msc
会打开服务窗口,在服务窗口中找到mysql服务,点击右键可以启动或者停止
方式2
以管理员身份运行cmd命令
停止命令:net stop mysql
启动命令:net start mysql
C:\Windows\system32>net stop mysql
mysql 服务正在停止.
mysql 服务已成功停止。
C:\Windows\system32>net start mysql
mysql 服务正在启动 .
mysql 服务已经启动成功。
注意:命令后面没有结束符号
mysql登录命令
mysql -h ip -P 端口 -u 用户名 -p
C:\Windows\system32>mysql -h localhost -P 3306 -u root -p
Enter password: *******
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 10
Server version: 5.7.25-log MySQL Community Server (GPL)
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
说明:
-P 大写的P后面跟上端口
如果是登录本金ip和端口可以省略,如:
mysql -u 用户名 -p
可以通过上面的命令连接原创机器的mysql
查看数据库版本
mysql --version 或者mysql -V
用于在未登录情况下,查看本机mysql版本:
C:\Windows\system32>mysql -V
mysql Ver 14.14 Distrib 5.7.25, for Win64 (x86_64)
C:\Windows\system32>mysql --version
mysql Ver 14.14 Distrib 5.7.25, for Win64 (x86_64)
select version();
:登录情况下,查看链接的库版本:
mysql> select version();
+------------+
| version() |
+------------+
| 5.7.25-log |
+------------+
1 row in set (0.00 sec)
显示所有数据库:show databases;
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| apolloconfigdb |
| apolloportaldb |
| config-server |
| dblog |
| diamond_devtest |
| mysql |
| nacos_config |
| performance_schema |
| rs_elastic_job |
| rs_master |
| seata |
| sys |
+--------------------+
13 rows in set (0.00 sec)
进入指定的库:use 库名;
mysql> use seata;
Database changed
显示当前库中所有的表:show tables;
mysql> show tables;
+--------------------+
| Tables_in_dblog |
+--------------------+
| biz_article |
| biz_article_look |
| biz_article_love |
| biz_article_tags |
| biz_comment |
| biz_file |
| biz_tags |
| biz_type |
| sys_config |
| sys_link |
| sys_log |
| sys_notice |
| sys_resources |
| sys_role |
| sys_role_resources |
| sys_template |
| sys_update_recorde |
| sys_user |
| sys_user_role |
+--------------------+
19 rows in set (0.00 sec)
查看其他库中所有的表:show tables from 库名;
mysql> show tables from seata;
+-----------------+
| Tables_in_seata |
+-----------------+
| branch_table |
| global_table |
| lock_table |
| t_account |
| t_order |
| t_storage |
| undo_log |
+-----------------+
7 rows in set (0.00 sec)
查看表的创建语句:show create table 表名;
mysql> show create table biz_tags;
+----------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+----------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| biz_tags | CREATE TABLE `biz_tags` (
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(50) NOT NULL COMMENT '书签名',
`description` varchar(100) DEFAULT NULL COMMENT '描述',
`create_time` datetime DEFAULT CURRENT_TIMESTAMP COMMENT '添加时间',
`update_time` datetime DEFAULT CURRENT_TIMESTAMP COMMENT '更新时间',
PRIMARY KEY (`id`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=21 DEFAULT CHARSET=utf8 ROW_FORMAT=COMPACT |
+----------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
查看表结构:desc 表名;
mysql> desc biz_tags;
+-------------+---------------------+------+-----+-------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+---------------------+------+-----+-------------------+----------------+
| id | bigint(20) unsigned | NO | PRI | NULL | auto_increment |
| name | varchar(50) | NO | | NULL | |
| description | varchar(100) | YES | | NULL | |
| create_time | datetime | YES | | CURRENT_TIMESTAMP | |
| update_time | datetime | YES | | CURRENT_TIMESTAMP | |
+-------------+---------------------+------+-----+-------------------+----------------+
5 rows in set (0.00 sec)
查看当前所在库:select database();
C:\Windows\system32>mysql -h localhost -P 3306 -u root -p
Enter password: *******
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 7
Server version: 5.7.25-log MySQL Community Server (GPL)
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> select database();
+------------+
| database() |
+------------+
| NULL |
+------------+
1 row in set (0.00 sec)
mysql> use dblog;
Database changed
mysql> select database();
+------------+
| database() |
+------------+
| dblog |
+------------+
1 row in set (0.00 sec)
查看当前mysql支持的存储引擎:SHOW ENGINES;
mysql> SHOW ENGINES;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine | Support | Comment | Transactions | XA | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |
| MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |
| CSV | YES | CSV storage engine | NO | NO | NO |
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |
| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.00 sec)
查看系统变量及其值:SHOW VARIABLES;
mysql> SHOW VARIABLES;
+----------------------------------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Variable_name | Value |
+----------------------------------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| auto_increment_increment | 1 |
| auto_increment_offset | 1 |
| autocommit | ON |
| automatic_sp_privileges | ON |
| avoid_temporal_upgrade | OFF |
| back_log | 90 |
| basedir | D:\installsoft\MySQL\mysql-5.7.25-winx64\ |
| big_tables | OFF |
| bind_address | * |
| binlog_cache_size | 32768 |
| binlog_checksum | CRC32 |
| binlog_direct_non_transactional_updates | OFF |
| binlog_error_action | ABORT_SERVER |
| binlog_format | ROW |
| binlog_group_commit_sync_delay | 0 |
| binlog_group_commit_sync_no_delay_count | 0 |
| binlog_gtid_simple_recovery | ON |
| 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 |
| binlog_transaction_dependency_history_size | 25000 |
| binlog_transaction_dependency_tracking | COMMIT_ORDER |
| block_encryption_mode | aes-128-ecb |
| bulk_insert_buffer_size | 8388608 |
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | utf8mb4 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | utf8 |
| character_set_system | utf8 |
| character_sets_dir | D:\installsoft\MySQL\mysql-5.7.25-winx64\share\charsets\ |
| check_proxy_users | OFF |
| collation_connection | utf8_general_ci |
| collation_database | utf8mb4_bin |
| collation_server | utf8_general_ci |
| completion_type | NO_CHAIN |
| concurrent_insert | AUTO |
| connect_timeout | 10 |
| core_file | OFF |
| datadir | D:\installsoft\MySQL\mysql-5.7.25-winx64\data\ |
| date_format | %Y-%m-%d |
| datetime_format | %Y-%m-%d %H:%i:%s |
| default_authentication_plugin | mysql_native_password |
| default_password_lifetime | 0 |
| default_storage_engine | InnoDB |
| default_tmp_storage_engine | InnoDB |
| default_week_format | 0 |
| delay_key_write | ON |
| delayed_insert_limit | 100 |
| delayed_insert_timeout | 300 |
| delayed_queue_size | 1000 |
| disabled_storage_engines | |
| disconnect_on_expired_password | ON |
| div_precision_increment | 4 |
| end_markers_in_json | OFF |
| enforce_gtid_consistency | OFF |
| eq_range_index_dive_limit | 200 |
| error_count | 0 |
| event_scheduler | OFF |
| expire_logs_days | 0 |
| explicit_defaults_for_timestamp | OFF |
| external_user | |
| flush | OFF |
| flush_time | 0 |
| foreign_key_checks | ON |
| ft_boolean_syntax | + -><()~*:""&| |
| ft_max_word_len | 84 |
| ft_min_word_len | 4 |
| ft_query_expansion_limit | 20 |
| ft_stopword_file | (built-in) |
| general_log | OFF |
| general_log_file | D:\installsoft\MySQL\mysql-5.7.25-winx64\data\DESKTOP-3OB6NA3.log |
| group_concat_max_len | 1024 |
| gtid_executed_compression_period | 1000 |
| gtid_mode | OFF |
| gtid_next | AUTOMATIC |
| gtid_owned | |
| gtid_purged | |
| have_compress | YES |
| have_crypt | NO |
| have_dynamic_loading | YES |
| have_geometry | YES |
| have_openssl | DISABLED |
| have_profiling | YES |
| have_query_cache | YES |
| have_rtree_keys | YES |
| have_ssl | DISABLED |
| have_statement_timeout | YES |
| have_symlink | YES |
| host_cache_size | 328 |
| hostname | DESKTOP-3OB6NA3 |
| identity | 0 |
| ignore_builtin_innodb | OFF |
| ignore_db_dirs | |
| init_connect | |
| init_file | |
| init_slave | |
| innodb_adaptive_flushing | ON |
| innodb_adaptive_flushing_lwm | 10 |
| innodb_adaptive_hash_index | ON |
| innodb_adaptive_hash_index_parts | 8 |
| innodb_adaptive_max_sleep_delay | 150000 |
| innodb_api_bk_commit_interval | 5 |
| innodb_api_disable_rowlock | OFF |
| innodb_api_enable_binlog | OFF |
| innodb_api_enable_mdl | OFF |
| innodb_api_trx_level | 0 |
| innodb_autoextend_increment | 64 |
| innodb_autoinc_lock_mode | 1 |
| innodb_buffer_pool_chunk_size | 134217728 |
| innodb_buffer_pool_dump_at_shutdown | ON |
| innodb_buffer_pool_dump_now | OFF |
| innodb_buffer_pool_dump_pct | 25 |
| innodb_buffer_pool_filename | ib_buffer_pool |
| innodb_buffer_pool_instances | 1 |
| innodb_buffer_pool_load_abort | OFF |
| innodb_buffer_pool_load_at_startup | ON |
| innodb_buffer_pool_load_now | OFF |
| innodb_buffer_pool_size | 134217728 |
| innodb_change_buffer_max_size | 25 |
| innodb_change_buffering | all |
| innodb_checksum_algorithm | crc32 |
| innodb_checksums | ON |
| innodb_cmp_per_index_enabled | OFF |
| innodb_commit_concurrency | 0 |
| innodb_compression_failure_threshold_pct | 5 |
| innodb_compression_level | 6 |
| innodb_compression_pad_pct_max | 50 |
| innodb_concurrency_tickets | 5000 |
| innodb_data_file_path | ibdata1:12M:autoextend |
| innodb_data_home_dir | |
| innodb_deadlock_detect | ON |
| innodb_default_row_format | dynamic |
| innodb_disable_sort_file_cache | OFF |
| innodb_doublewrite | ON |
| innodb_fast_shutdown | 1 |
| innodb_file_format | Barracuda |
| innodb_file_format_check | ON |
| innodb_file_format_max | Barracuda |
| innodb_file_per_table | ON |
| innodb_fill_factor | 100 |
| innodb_flush_log_at_timeout | 1 |
| innodb_flush_log_at_trx_commit | 1 |
| innodb_flush_method | |
| innodb_flush_neighbors | 1 |
| innodb_flush_sync | ON |
| innodb_flushing_avg_loops | 30 |
| innodb_force_load_corrupted | OFF |
| innodb_force_recovery | 0 |
| innodb_ft_aux_table | |
| innodb_ft_cache_size | 8000000 |
| innodb_ft_enable_diag_print | OFF |
| innodb_ft_enable_stopword | ON |
| innodb_ft_max_token_size | 84 |
| innodb_ft_min_token_size | 3 |
| innodb_ft_num_word_optimize | 2000 |
| innodb_ft_result_cache_limit | 2000000000 |
| innodb_ft_server_stopword_table | |
| innodb_ft_sort_pll_degree | 2 |
| innodb_ft_total_cache_size | 640000000 |
| innodb_ft_user_stopword_table | |
| innodb_io_capacity | 200 |
| innodb_io_capacity_max | 2000 |
| innodb_large_prefix | ON |
| innodb_lock_wait_timeout | 50 |
| innodb_locks_unsafe_for_binlog | OFF |
| innodb_log_buffer_size | 16777216 |
| innodb_log_checksums | ON |
| innodb_log_compressed_pages | ON |
| innodb_log_file_size | 50331648 |
| innodb_log_files_in_group | 2 |
| innodb_log_group_home_dir | .\ |
| innodb_log_write_ahead_size | 8192 |
| innodb_lru_scan_depth | 1024 |
| innodb_max_dirty_pages_pct | 75.000000 |
| innodb_max_dirty_pages_pct_lwm | 0.000000 |
| innodb_max_purge_lag | 0 |
| innodb_max_purge_lag_delay | 0 |
| innodb_max_undo_log_size | 1073741824 |
| innodb_monitor_disable | |
| innodb_monitor_enable | |
| innodb_monitor_reset | |
| innodb_monitor_reset_all | |
| innodb_old_blocks_pct | 37 |
| innodb_old_blocks_time | 1000 |
| innodb_online_alter_log_max_size | 134217728 |
| innodb_open_files | 2000 |
| innodb_optimize_fulltext_only | OFF |
| innodb_page_cleaners | 1 |
| innodb_page_size | 16384 |
| innodb_print_all_deadlocks | OFF |
| innodb_purge_batch_size | 300 |
| innodb_purge_rseg_truncate_frequency | 128 |
| innodb_purge_threads | 4 |
| innodb_random_read_ahead | OFF |
| innodb_read_ahead_threshold | 56 |
| innodb_read_io_threads | 4 |
| innodb_read_only | OFF |
| innodb_replication_delay | 0 |
| innodb_rollback_on_timeout | OFF |
| innodb_rollback_segments | 128 |
| innodb_sort_buffer_size | 1048576 |
| innodb_spin_wait_delay | 6 |
| innodb_stats_auto_recalc | ON |
| innodb_stats_include_delete_marked | OFF |
| innodb_stats_method | nulls_equal |
| innodb_stats_on_metadata | OFF |
| innodb_stats_persistent | ON |
| innodb_stats_persistent_sample_pages | 20 |
| innodb_stats_sample_pages | 8 |
| innodb_stats_transient_sample_pages | 8 |
| innodb_status_output | ON |
| innodb_status_output_locks | ON |
| innodb_strict_mode | ON |
| innodb_support_xa | ON |
| innodb_sync_array_size | 1 |
| innodb_sync_spin_loops | 30 |
| innodb_table_locks | ON |
| innodb_temp_data_file_path | ibtmp1:12M:autoextend |
| innodb_thread_concurrency | 0 |
| innodb_thread_sleep_delay | 10000 |
| innodb_tmpdir | |
| innodb_undo_directory | .\ |
| innodb_undo_log_truncate | OFF |
| innodb_undo_logs | 128 |
| innodb_undo_tablespaces | 0 |
| innodb_use_native_aio | ON |
| innodb_version | 5.7.25 |
| innodb_write_io_threads | 4 |
| insert_id | 0 |
| interactive_timeout | 28800 |
| internal_tmp_disk_storage_engine | InnoDB |
| join_buffer_size | 262144 |
| keep_files_on_create | OFF |
| key_buffer_size | 8388608 |
| key_cache_age_threshold | 300 |
| key_cache_block_size | 1024 |
| key_cache_division_limit | 100 |
| keyring_operations | ON |
| large_files_support | ON |
| large_page_size | 0 |
| large_pages | OFF |
| last_insert_id | 0 |
| lc_messages | en_US |
| lc_messages_dir | D:\installsoft\MySQL\mysql-5.7.25-winx64\share\ |
| lc_time_names | en_US |
| license | GPL |
| local_infile | ON |
| lock_wait_timeout | 31536000 |
| log_bin | ON |
| log_bin_basename | D:\installsoft\MySQL\mysql-5.7.25-winx64\data\mysql_bin |
| log_bin_index | D:\installsoft\MySQL\mysql-5.7.25-winx64\data\mysql_bin.index |
| log_bin_trust_function_creators | OFF |
| log_bin_use_v1_row_events | OFF |
| log_builtin_as_identified_by_password | OFF |
| log_error | D:\installsoft\MySQL\mysql-5.7.25-winx64\data\DESKTOP-3OB6NA3.err |
| log_error_verbosity | 3 |
| log_output | FILE |
| log_queries_not_using_indexes | OFF |
| log_slave_updates | OFF |
| log_slow_admin_statements | OFF |
| log_slow_slave_statements | OFF |
| log_statements_unsafe_for_binlog | ON |
| log_syslog | ON |
| log_syslog_tag | |
| log_throttle_queries_not_using_indexes | 0 |
| log_timestamps | UTC |
| log_warnings | 2 |
| long_query_time | 0.000000 |
| low_priority_updates | OFF |
| lower_case_file_system | ON |
| lower_case_table_names | 1 |
| master_info_repository | FILE |
| master_verify_checksum | OFF |
| max_allowed_packet | 4194304 |
| max_binlog_cache_size | 18446744073709547520 |
| max_binlog_size | 1073741824 |
| max_binlog_stmt_cache_size | 18446744073709547520 |
| max_connect_errors | 100 |
| max_connections | 200 |
| max_delayed_threads | 20 |
| max_digest_length | 1024 |
| max_error_count | 64 |
| max_execution_time | 0 |
| max_heap_table_size | 16777216 |
| max_insert_delayed_threads | 20 |
| max_join_size | 18446744073709551615 |
| max_length_for_sort_data | 1024 |
| max_points_in_geometry | 65536 |
| max_prepared_stmt_count | 16382 |
| max_relay_log_size | 0 |
| max_seeks_for_key | 4294967295 |
| max_sort_length | 1024 |
| max_sp_recursion_depth | 0 |
| max_tmp_tables | 32 |
| max_user_connections | 0 |
| max_write_lock_count | 4294967295 |
| metadata_locks_cache_size | 1024 |
| metadata_locks_hash_instances | 8 |
| min_examined_row_limit | 0 |
| multi_range_count | 256 |
| myisam_data_pointer_size | 6 |
| myisam_max_sort_file_size | 2146435072 |
| myisam_mmap_size | 18446744073709551615 |
| myisam_recover_options | OFF |
| myisam_repair_threads | 1 |
| myisam_sort_buffer_size | 8388608 |
| myisam_stats_method | nulls_unequal |
| myisam_use_mmap | OFF |
| mysql_native_password_proxy_users | OFF |
| named_pipe | OFF |
| named_pipe_full_access_group | *everyone* |
| net_buffer_length | 16384 |
| net_read_timeout | 30 |
| net_retry_count | 10 |
| net_write_timeout | 60 |
| new | OFF |
| ngram_token_size | 2 |
| offline_mode | OFF |
| old | OFF |
| old_alter_table | OFF |
| old_passwords | 0 |
| open_files_limit | 7048 |
| optimizer_prune_level | 1 |
| optimizer_search_depth | 62 |
| optimizer_switch | index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,duplicateweedout=on,subquery_materialization_cost_based=on,use_index_extensions=on,condition_fanout_filter=on,derived_merge=on |
| optimizer_trace | enabled=off,one_line=off |
| optimizer_trace_features | greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on |
| optimizer_trace_limit | 1 |
| optimizer_trace_max_mem_size | 16384 |
| optimizer_trace_offset | -1 |
| parser_max_mem_size | 18446744073709551615 |
| performance_schema | ON |
| performance_schema_accounts_size | -1 |
| performance_schema_digests_size | 10000 |
| performance_schema_events_stages_history_long_size | 10000 |
| performance_schema_events_stages_history_size | 10 |
| performance_schema_events_statements_history_long_size | 10000 |
| performance_schema_events_statements_history_size | 10 |
| performance_schema_events_transactions_history_long_size | 10000 |
| performance_schema_events_transactions_history_size | 10 |
| performance_schema_events_waits_history_long_size | 10000 |
| performance_schema_events_waits_history_size | 10 |
| performance_schema_hosts_size | -1 |
| performance_schema_max_cond_classes | 80 |
| performance_schema_max_cond_instances | -1 |
| performance_schema_max_digest_length | 1024 |
| performance_schema_max_file_classes | 80 |
| performance_schema_max_file_handles | 32768 |
| performance_schema_max_file_instances | -1 |
| performance_schema_max_index_stat | -1 |
| performance_schema_max_memory_classes | 320 |
| performance_schema_max_metadata_locks | -1 |
| performance_schema_max_mutex_classes | 210 |
| performance_schema_max_mutex_instances | -1 |
| performance_schema_max_prepared_statements_instances | -1 |
| performance_schema_max_program_instances | -1 |
| performance_schema_max_rwlock_classes | 50 |
| performance_schema_max_rwlock_instances | -1 |
| performance_schema_max_socket_classes | 10 |
| performance_schema_max_socket_instances | -1 |
| performance_schema_max_sql_text_length | 1024 |
| performance_schema_max_stage_classes | 150 |
| performance_schema_max_statement_classes | 193 |
| performance_schema_max_statement_stack | 10 |
| performance_schema_max_table_handles | -1 |
| performance_schema_max_table_instances | -1 |
| performance_schema_max_table_lock_stat | -1 |
| performance_schema_max_thread_classes | 50 |
| performance_schema_max_thread_instances | -1 |
| performance_schema_session_connect_attrs_size | 512 |
| performance_schema_setup_actors_size | -1 |
| performance_schema_setup_objects_size | -1 |
| performance_schema_users_size | -1 |
| pid_file | D:\installsoft\MySQL\mysql-5.7.25-winx64\data\DESKTOP-3OB6NA3.pid |
| plugin_dir | D:\installsoft\MySQL\mysql-5.7.25-winx64\lib\plugin\ |
| port | 3306 |
| preload_buffer_size | 32768 |
| profiling | OFF |
| profiling_history_size | 15 |
| protocol_version | 10 |
| proxy_user | |
| pseudo_slave_mode | OFF |
| pseudo_thread_id | 2 |
| query_alloc_block_size | 8192 |
| query_cache_limit | 1048576 |
| query_cache_min_res_unit | 4096 |
| query_cache_size | 1048576 |
| query_cache_type | OFF |
| query_cache_wlock_invalidate | OFF |
| query_prealloc_size | 8192 |
| rand_seed1 | 0 |
| rand_seed2 | 0 |
| range_alloc_block_size | 4096 |
| range_optimizer_max_mem_size | 8388608 |
| rbr_exec_mode | STRICT |
| read_buffer_size | 131072 |
| read_only | OFF |
| read_rnd_buffer_size | 262144 |
| relay_log | |
| relay_log_basename | D:\installsoft\MySQL\mysql-5.7.25-winx64\data\DESKTOP-3OB6NA3-relay-bin |
| relay_log_index | D:\installsoft\MySQL\mysql-5.7.25-winx64\data\DESKTOP-3OB6NA3-relay-bin.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 |
| report_host | |
| report_password | |
| report_port | 3306 |
| report_user | |
| require_secure_transport | OFF |
| rpl_stop_slave_timeout | 31536000 |
| secure_auth | ON |
| secure_file_priv | NULL |
| server_id | 1 |
| server_id_bits | 32 |
| server_uuid | 5535390b-40a4-11e9-af3e-e86a64887726 |
| session_track_gtids | OFF |
| session_track_schema | ON |
| session_track_state_change | OFF |
| session_track_system_variables | time_zone,autocommit,character_set_client,character_set_results,character_set_connection |
| session_track_transaction_info | OFF |
| sha256_password_proxy_users | OFF |
| shared_memory | OFF |
| shared_memory_base_name | MYSQL |
| show_compatibility_56 | OFF |
| show_create_table_verbosity | OFF |
| show_old_temporals | OFF |
| skip_external_locking | ON |
| skip_name_resolve | OFF |
| skip_networking | OFF |
| skip_show_database | OFF |
| slave_allow_batching | OFF |
| slave_checkpoint_group | 512 |
| slave_checkpoint_period | 300 |
| slave_compressed_protocol | OFF |
| slave_exec_mode | STRICT |
| slave_load_tmpdir | C:\Windows\TEMP |
| slave_max_allowed_packet | 1073741824 |
| slave_net_timeout | 60 |
| slave_parallel_type | DATABASE |
| slave_parallel_workers | 0 |
| slave_pending_jobs_size_max | 16777216 |
| slave_preserve_commit_order | OFF |
| slave_rows_search_algorithms | TABLE_SCAN,INDEX_SCAN |
| slave_skip_errors | OFF |
| slave_sql_verify_checksum | ON |
| slave_transaction_retries | 10 |
| slave_type_conversions | |
| slow_launch_time | 2 |
| slow_query_log | ON |
| slow_query_log_file | D:/installsoft/MySQL/mysql-5.7.25-winx64/log/slow.log |
| socket | MySQL |
| sort_buffer_size | 262144 |
| sql_auto_is_null | OFF |
| sql_big_selects | ON |
| sql_buffer_result | OFF |
| sql_log_bin | ON |
| sql_log_off | OFF |
| sql_mode | ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
| sql_notes | ON |
| sql_quote_show_create | ON |
| sql_safe_updates | OFF |
| sql_select_limit | 18446744073709551615 |
| sql_slave_skip_counter | 0 |
| sql_warnings | OFF |
| ssl_ca | |
| ssl_capath | |
| ssl_cert | |
| ssl_cipher | |
| ssl_crl | |
| ssl_crlpath | |
| ssl_key | |
| stored_program_cache | 256 |
| super_read_only | OFF |
| sync_binlog | 1 |
| sync_frm | ON |
| sync_master_info | 10000 |
| sync_relay_log | 10000 |
| sync_relay_log_info | 10000 |
| system_time_zone | |
| table_definition_cache | 1400 |
| table_open_cache | 2000 |
| table_open_cache_instances | 16 |
| thread_cache_size | 10 |
| thread_handling | one-thread-per-connection |
| thread_stack | 262144 |
| time_format | %H:%i:%s |
| time_zone | SYSTEM |
| timestamp | 1566971784.132916 |
| tls_version | TLSv1,TLSv1.1 |
| tmp_table_size | 16777216 |
| tmpdir | C:\Windows\TEMP |
| transaction_alloc_block_size | 8192 |
| transaction_allow_batching | OFF |
| transaction_isolation | READ-COMMITTED |
| transaction_prealloc_size | 4096 |
| transaction_read_only | OFF |
| transaction_write_set_extraction | OFF |
| tx_isolation | READ-COMMITTED |
| tx_read_only | OFF |
| unique_checks | ON |
| updatable_views_with_limit | YES |
| version | 5.7.25-log |
| version_comment | MySQL Community Server (GPL) |
| version_compile_machine | x86_64 |
| version_compile_os | Win64 |
| wait_timeout | 28800 |
| warning_count | 0 |
+----------------------------------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
513 rows in set, 1 warning (0.00 sec)
查看某个系统变量:SHOW VARIABLES like ‘变量名’;
mysql> SHOW VARIABLES like 'wait_timeout';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| wait_timeout | 28800 |
+---------------+-------+
1 row in set, 1 warning (0.00 sec)
mysql> SHOW VARIABLES like '%wait_timeou%t';
+--------------------------+----------+
| Variable_name | Value |
+--------------------------+----------+
| innodb_lock_wait_timeout | 50 |
| lock_wait_timeout | 31536000 |
| wait_timeout | 28800 |
+--------------------------+----------+
3 rows in set, 1 warning (0.00 sec)
mysql语法规范
- 不区分大小写,但建议关键字大写,表名、列名小写
- 每条命令最好用英文分号结尾
- 每条命令根据需要,可以进行缩进或换行
- 注释
- 单行注释:#注释文字
- 单行注释:— 注释文字 ,注意, 这里需要加空格
- 多行注释:/ 注释文字 /
SQL的语言分类
- DQL(Data Query Language):数据查询语言
select 相关语句 - DML(Data Manipulate Language):数据操作语言
insert 、update、delete 语句 - DDL(Data Define Languge):数据定义语言
create、drop、alter 语句 - TCL(Transaction Control Language):事务控制语言
set autocommit=0、start transaction、savepoint、commit、rollback
最新资料
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