时间：2021-07-01 10:21:17 帮助过：17人阅读
# 增 create database review; # 查 show databases; show create database review; # 查看数据库的创建，默认为 CHARACTER SET latin1 编码 # 改 # 没有专门的改操作，删了重建 alter database review charset utf8; # 将数据库的字符编码改为utf8编码 # 删 drop database review;
use review;
# 增（创建）
create table test (
id int auto_increment primary key,
name varchar(32) not null default ‘‘
)engine=Innodb charset=utf8;
create table test_join (
id int auto_increment primary key,
course varchar(32) not null default ‘‘,
name_join int not null default 0,
constraint fk_name_id foreign key (name_join) references test(id)
)engine=Innodb charset=utf8;
# 删
drop table test;
alter table test drop name; # 删除列/字段名
# 改
alter table test rename new_test; # 更改表名
alter table test change/modify name title varchar(32) not null default ‘‘; # 修改字段名
alter table test add title varchar(32) not null default ‘‘; # 增加新列
# 查
show tables;
# 增 insert into test (name) values (‘wangyong‘), (‘liguo‘), (‘jiyuzhi‘); # 删 delete from test where id=3; delete from test; # 删除之后，增加数据id会直接增加 truncate test; # 删除之后，增加数据id会清空 # 改 update test set name=‘title‘; # 将name属性的值全部改为title update test set name=‘title‘ where id=2; # 将id=2d的name属性的值改为title # 查 select * from test; select name from test;
# where select * from test where id>1 and id<=3; # between and 闭区间 select * from test where id between 1 and 3; # in / not in select * from test where id in (1,2,3); # 通配符 select * from test where name like ‘%wang%‘; select * from test where name like ‘%wang_‘; # limit select * from 表名 limit 索引偏移量, 取出多少条数据; select * from test where id limit 2,3; # 从第2号位（第3个数）开始查询3个 # group by 分组 # select age, 聚合函数(count(num)/sum(num)/max(num)/min(num)/avg(num)) from 表名 group by 列名; select name, count(name) from test group by name; select name, count(name) from test group by name having name=‘wangyong‘; # 二次筛选 # order by 排序 select * from test order by name desc; # desc:降序 select * from test order by name asc; # asc:升序 # 连表（left join、 right join、 inner join） # left join 左边的表全部显示, 右边没有用到不显示 select test.name, test_join.course from test left join test_join on test.id=test_join.name_join;
自己手动去判断转义用户输入的数据
不要拼接SQL语句, 使用PyMySQL中的execute方法, 防止SQL的注入
import pymysql
gender = input(‘gender>>>:‘)
sname = input("sname>>>:")
# 链接服务器
conn = pymysql.connect(host = ‘localhost‘, user = ‘root‘, password = ‘‘, database = ‘practiceday43‘, charset = ‘utf8‘ )
cursor = conn.cursor(cursor = pymysql.cursors.DictCursor)
# 写SQL语句，不要去拼接SQL语句
sql = "select * from student where gender = %s and sname = %s"
# 传值的时候，以元组形式给SQL传参
cursor.execute(sql,(gender, sname))
res = cursor.fetchone()
print(res)
if res:
print(‘获得值成功‘)
else:
print(‘获得值失败‘)
cursor.close()
conn.close()
原子性: 一组操作, 要么全部成功, 要么全部失败 一致性: 操作之前和操作之后, 总的金额是一致的 隔离性: 本次事物的操作对其他事务的操作是没有任何影响的 持久性: 当我们commit/rollback之后, 影响就已经生效了, 补偿性事务来解决
开启: start transaction 一组SQL语句的操作 完成(commit/rollback)
create table user( id int auto_increment primary key, name varchar(32) not null default ‘‘, money int not null default 1000 )engine=innodb charset=utf8; insert into user (name,money) values (‘wangyong‘,1000),(‘liguo‘,1000); # 正常操作 start transaction; update user set money=1100 where name=‘wangyong‘; updata user set money=900 where name=‘liguo‘; # 出现异常 rollback; # 最终结果， 数据未发生变化 mysql> select * from user; +----+----------+-------+ | id | name | money | +----+----------+-------+ | 1 | wangyong | 1000 | | 2 | liguo | 1000 | +----+----------+-------+
# 第一种:
create table test(
id int auto_increment primary key,
name varchar(32) not null default ‘‘
)engine=innodb charset=utf8;
# 第二种：
create table test(
id int not null default 0,
name varchar(32) not null default ‘‘
)engine=innodb charset=utf8;
alter table test change id id int auto_increment primary key;
# 第一种
create table test(
id int auto_increment primary key,
name varchar(32) not null default ‘‘,
unique ix_name (name)
)engine=innodb charset=utf8;
# 第二种 create unique index 索引名称 on 表名(name);
create table test(
id int auto_increment primary key,
name varchar(32) not null default ‘‘
)engine=innodb charset=utf8;
create unique index ix_name on test (name);
# 创建联合唯一索引 create unique index 索引名称 on 表名 (name,age);
create table test(
id int auto_increment primary key,
age int not null default 0,
name varchar(32) not null default ‘‘
)engine=innodb charset=utf8;
create unique index ix_name_age on test (age, name);
# 第一种
create table test(
id int auto_increment primary key,
name varchar(32) not null default ‘‘,
index ix_name (name)
)engine=innodb charset=utf8;
# 第二种
create table test(
id int auto_increment primary key,
name varchar(32) not null default ‘‘
)engine=innodb charset=utf8;
create index ix_name on test (name);
# 联合索引
create table test(
id int auto_increment primary key,
age int not null default 0,
name varchar(32) not null default ‘‘
)engine=innodb charset=utf8;
create index ix_name_age on test (age, name);
explain selext * from test; +----+-------------+-------+-------+---------------+---------+---------+------+------+------------- | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra +----+-------------+-------+-------+---------------+---------+---------+------+------+------------- | 1 | SIMPLE | test | index | NULL | ix_name | 98 | NULL | 1 | Using index +----+-------------+-------+-------+---------------+---------+---------+------+------+-------------
- 不建议使用 like 进行搜索
- 组合索引最左前缀
如果组合索引为：(name,email)
where name and email -- 使用索引
where name -- 使用索引
where email -- 不使用索引
# drop 索引名称 on 表名 drop index ix_name_age on test; mysql> explain select * from test; +----+-------------+-------+------+---------------+------+---------+------+------+-------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+------+-------+ | 1 | SIMPLE | test | ALL | NULL | NULL | NULL | NULL | 1 | NULL | +----+-------------+-------+------+---------------+------+---------+------+------+-------+
Innodb(支持高并发)
1.(默认版本包含5.5)
2.支持事务
3.不支持全文索引
4.索引和数据都是在同一个文件中, .ibd 表的结构实在.frm文件中
MyIsam（支持高并发不是特别理想）
1.(默认版本5.5以下 5.3)
2.不支持事务
3.支持全文索引
4..frm: 表结构
.MYD: 表数据
.MYI: 表索引
全文索引:（中文很好）
sphinx
python第四十六天 数据库总结
标签：port where rev 通配 inno 持久性 tar char 四十