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 mysqlmysql 服务正在停止.mysql 服务已成功停止。C:\Windows\system32>net start mysqlmysql 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 -pEnter password: *******Welcome to the MySQL monitor. Commands end with ; or \g.Your MySQL connection id is 10Server 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 itsaffiliates. Other names may be trademarks of their respectiveowners.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 -Vmysql Ver 14.14 Distrib 5.7.25, for Win64 (x86_64)C:\Windows\system32>mysql --versionmysql 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 -pEnter password: *******Welcome to the MySQL monitor. Commands end with ; or \g.Your MySQL connection id is 7Server 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 itsaffiliates. Other names may be trademarks of their respectiveowners.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 changedmysql> 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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