Vérification rapide MySQL
Parce que j'oublie souvent certaines instructions, mots-clés, opérations, etc. MySQL dans mon travail et mes études quotidiens, j'ai récemment pris le temps d'écrire le contenu suivant sur MySQL. C'est comme un dictionnaire
Réinitialiser le mot de passe MySQL Opérateur
de type de données Fonctions communes Opérations de base de la base de données d'intégrité des données Cet article opère sur les données de la table Sous-requête Connexion multi-table Vue index Prétraitement des instructions SQL Fonctions personnalisées et procédures stockées Programmation dans MySQL
Opérations sur la table elle-même
Voir le tableau
Voir tout
1 show tables;
2 SHOW TABLE STATUS
[{
FROM | IN} 数据库名]
[LIKE 'pattern' | WHERE where筛选表达式]
show table status类似show tables，但会显示更多信息
mysql> show table status from sys;
+-----------------------------------------------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+-------------+------------+--------------------+----------+----------------+---------+
| Name | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length | Index_length | Data_free | Auto_increment | Create_time | Update_time | Check_time | Collation | Checksum | Create_options | Comment |
+-----------------------------------------------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+-------------+------------+--------------------+----------+----------------+---------+
| host_summary | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | 2021-03-08 19:30:21 | NULL | NULL | NULL | NULL | NULL | VIEW |
| host_summary_by_file_io | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | 2021-03-08 19:30:21 | NULL | NULL | NULL | NULL | NULL | VIEW |
...
# 使用show tables时
mysql> use sys;
mysql> show tables;
+-----------------------------------------------+
| Tables_in_sys |
+-----------------------------------------------+
| host_summary |
| host_summary_by_file_io |
| host_summary_by_file_io_type |
...
Afficher la structure du tableau
1 describe tb_name;
desc是describe的缩写
# 查看表结构详细信息
2 show create table 表名;
mysql> use sys;
mysql> desc host_summary;
+------------------------+---------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------------+---------------+------+-----+---------+-------+
| host | varchar(255) | YES | | NULL | |
...
mysql> show create table host_summary;
+--------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
| View | Create View | character_set_client | collation_connection |
+--------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
| host_summary | CREATE ALGORITHM=TEMPTABLE DEFINER=`mysql.sys`@`localhost` SQL SECURITY INVOKER VIEW `host_summary` (`host`,`statements`,`statement_latency`,`statement_avg_latency`,`table_scans`,`file_ios`,`file_io_latency`,`current_connections`,`total_connections`,`unique_users`,`current_memory`,`total_memory_allocated`) AS select if((`performance_schema`.`accounts`.`HOST` is null),'background',`performance_schema`.`accounts`.`HOST`) AS `host`,sum(`stmt`.`total`) AS `statements`,format_pico_time(sum(`stmt`.`total_latency`)) AS `statement_latency`,format_pico_time(ifnull((sum(`stmt`.`total_latency`) / nullif(sum(`stmt`.`total`),0)),0)) AS `statement_avg_latency`,sum(`stmt`.`full_scans`) AS `table_scans`,sum(`io`.`ios`) AS `file_ios`,format_pico_time(sum(`io`.`io_latency`)) AS `file_io_latency`,sum(`performance_schema`.`accounts`.`CURRENT_CONNECTIONS`) AS `current_connections`,sum(`performance_schema`.`accounts`.`TOTAL_CONNECTIONS`) AS `total_connections`,count(distinct `performance_schema`.`accounts`.`USER`) AS `unique_users`,format_bytes(sum(`mem`.`current_allocated`)) AS `current_memory`,format_bytes(sum(`mem`.`total_allocated`)) AS `total_memory_allocated` from (((`performance_schema`.`accounts` join `x$host_summary_by_statement_latency` `stmt` on((`performance_schema`.`accounts`.`HOST` = `stmt`.`host`))) join `x$host_summary_by_file_io` `io` on((`performance_schema`.`accounts`.`HOST` = `io`.`host`))) join `x$memory_by_host_by_current_bytes` `mem` on((`performance_schema`.`accounts`.`HOST` = `mem`.`host`))) group by if((`performance_schema`.`accounts`.`HOST` is null),'background',`performance_schema`.`accounts`.`HOST`) | utf8mb4 | utf8mb4_0900_ai_ci |
+--------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
1 row in set (0.01 sec)
Ajouter un tableau
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] 表名
(字段名 数据类型 [完整性约束],...)
如果指定temporary，则创建的是临时表，
会话结束会自动释放，并且show tables看不到该表
mysql> use test;
Database changed
mysql> show tables;
Empty set (0.00 sec)
mysql> create table t1(id int primary key, name char(10));
Query OK, 0 rows affected (0.12 sec)
mysql> desc t1;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| id | int | NO | PRI | NULL | |
| name | char(10) | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
2 rows in set (0.00 sec)
Supprimer le tableau
DROP [TEMPORARY] TABLE [IF EXISTS]
表名1 [, 表名2] ...
[RESTRICT | CASCADE]
Les mots-clés RESTRICT et CASCADE n'ont aucun effet. Ces deux mots-clés sont utilisés pour faciliter la portabilité depuis d'autres bases de données.
La suppression d'un tableau supprimera également les données du tableau.
drop table t1; # 删除t1表
Modifier le tableau
Modifier les champs dans le tableau
ALTER TABLE 表名
[alter_option [, alter_option] ...]
[partition_options]
alter_option: alter操作，如增加、删除、修改等，下面详细介绍。
partition_options: 分区操作
Ajouter le champ
ALTER TABLE 表名
ADD [COLUMN] 要增加的字段名 数据类型 完整性约束
[FIRST | AFTER 表中存在的字段名]
# 例如
alter table t1
add column sex char(1) not null default '女'
after name;
d'abord et après spécifiez la position du nouveau champ. S'il n'est pas écrit, il sera ajouté à la fin par défaut. (Remarque : n'ajoutez aucun caractère après le premier)
Vous pouvez également ajouter plusieurs champs en même temps.
ALTER TABLE 表名
ADD [COLUMN] 要增加的字段名 数据类型 完整性约束[,...]
# 例如
alter table t1
add sex char(1) default '男',
age int;
Ajouter/supprimer des contraintes d'intégrité pour les champs de la table
ALTER TABLE 表名
# 添加主键
ADD PRIMARY KEY(字段名,...)
# 为字段指定唯一约束
| ADD UNIQUE (字段名,...)
# 添加外键
| ADD FOREIGN KEY(字段名,...)
references 另一个表名(字段名,...)
# 为字段增加check约束
| ADD CHECK (expr)
# 为字段删除check
| DROP CHECK symbol
# 去除字段主键约束
| DROP PRIMARY KEY
# 去除字段外键约束
| DROP FOREIGN KEY fk_symbol
Modifier les champs
champ changerModifier
ALTER TABLE 表名
CHANGE [COLUMN] 旧字段名 新字段名 数据类型 完整性约束
[FIRST | AFTER 表中字段名]
mysql> desc t1;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| id | int | NO | PRI | NULL | |
| name | char(10) | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
2 rows in set (0.00 sec)
mysql> desc t1;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| id | int | NO | PRI | NULL | |
| name | char(10) | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
2 rows in set (0.01 sec)
mysql> alter table t1
-> change name xingming varchar(12) not null
-> first; # 将name改成xingming并放在首位
Query OK, 0 rows affected (0.26 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc t1;
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| xingming | varchar(12) | NO | | NULL | |
| id | int | NO | PRI | NULL | |
+----------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
modifier modifier le champ
ALTER TABLE 表名
MODIFY [COLUMN]
字段名 新数据类型 [新完整性约束]
[FIRST | AFTER 字段名]
alter table t1
modify column
xingming char(10) unique
after id;
mysql> alter table t1
-> modify column
-> xingming char(10) unique
-> after id;
Query OK, 0 rows affected (0.21 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc t1;
+----------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------+------+-----+---------+-------+
| id | int | NO | PRI | NULL | |
| xingming | char(10) | YES | UNI | NULL | |
+----------+----------+------+-----+---------+-------+
2 rows in set (0.00 sec)
renommerRenommer le champ
ALTER TABLE 表名
RENAME COLUMN 旧字段名 TO 新字段名
mysql> alter table t1 rename column xingming to name;
Query OK, 0 rows affected (0.02 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc t1;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| id | int | NO | PRI | NULL | |
| name | char(10) | YES | UNI | NULL | |
+-------+----------+------+-----+---------+-------+
2 rows in set (0.00 sec)
Supprimer le champ
ALTER TABLE 表名 DROP [COLUMN] 字段名
alter table t1 drop name;
Modifier le nom de la table
ALTER TABLE 表名 RENAME [TO | AS] 新表名
mysql> alter table t1 rename to t2;
Query OK, 0 rows affected (0.02 sec)
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| t2 |
+----------------+
1 row in set (0.00 sec)
mysql> alter table t2 rename as t1;
Query OK, 0 rows affected (0.02 sec)
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| t1 |
+----------------+
1 row in set (0.00 sec)