1.数据库知识结构
建立索引： - a. 额外的文件保存特殊的数据结构、 - b. 查询快；插入更新删除慢 - c. 命中索引 select * from userinfo3 where email='asdf'; select * from userinfo3 where email like 'asdf'; 慢 ... 主键索引： 普通索引： - create index 索引名称 on 表名(列名,) - drop index 索引名称 on 表名 唯一索引： - create unique index 索引名称 on 表名(列名) - drop unique index 索引名称 on 表名 组合索引(最左前缀匹配)： - create unique index 索引名称 on 表名(列名,列名) - drop unique index 索引名称 on 表名 - create index ix_name_email on userinfo3(name,email,) - 最左前缀匹配 select * from userinfo3 where name='alex'; select * from userinfo3 where name='alex' and email='asdf'; select * from userinfo3 where email='alex@qq.com'; 组合索引效率 > 索引合并 组合索引 - (name,email,) select * from userinfo3 where name='alex' and email='asdf'; select * from userinfo3 where name='alex'; 索引合并： - name - email select * from userinfo3 where name='alex' and email='asdf'; select * from userinfo3 where name='alex'; select * from userinfo3 where email='alex'; 名词： 覆盖索引： - 在索引文件中直接获取数据 索引合并： - 把多个单列索引合并使用 2. 频繁查找的列创建索引 - 创建索引 - 命中索引 ***** - like '%xx' select * from tb1 where email like '%cn'; - 使用函数 select * from tb1 where reverse(email) = 'wupeiqi'; - or select * from tb1 where nid = 1 or name = 'seven@live.com'; 特别的：当or条件中有未建立索引的列才失效，以下会走索引 select * from tb1 where nid = 1 or name = 'seven'; select * from tb1 where nid = 1 or name = 'seven@live.com' and email = 'alex' - 类型不一致 如果列是字符串类型，传入条件是必须用引号引起来，不然... select * from tb1 where email = 999; - != select * from tb1 where email != 'alex' 特别的：如果是主键，则还是会走索引 select * from tb1 where nid != 123 - > select * from tb1 where email > 'alex' 特别的：如果是主键或索引是整数类型，则还是会走索引 select * from tb1 where nid > 123 select * from tb1 where num > 123 - order by select name from tb1 order by email desc; 当根据索引排序时候，选择的映射如果不是索引，则不走索引 特别的：如果对主键排序，则还是走索引： select * from tb1 order by nid desc; - 组合索引最左前缀 如果组合索引为：(name,email) name and email -- 使用索引 name -- 使用索引 email -- 不使用索引 3. 时间 执行计划：让mysql预估执行操作(一般正确) all < index < range < index_merge < ref_or_null < ref < eq_ref < system/const id,email 慢： select * from userinfo3 where name='alex' explain select * from userinfo3 where name='alex' type: ALL(全表扫描) select * from userinfo3 limit 1; 快： select * from userinfo3 where email='alex' type: const(走索引) 4. DBA工作 慢日志 - 执行时间 > 10 - 未命中索引 - 日志文件路径 配置： - 内存 show variables like '%query%' set global 变量名 = 值 - 配置文件 mysqld --defaults-file='E:wupeiqimysql-5.7.16-winx64mysql-5.7.16-winx64my-default.ini' my.conf内容： slow_query_log = ON slow_query_log_file = D:/.... 注意：修改配置文件之后，需要重启服务 5. ******分页******* a. select * from userinfo3 limit 20,10; b. - 不让看 - 索引表中扫： select * from userinfo3 where id in(select id from userinfo3 limit 200000,10) - 方案： 记录当前页最大或最小ID 1. 页面只有上一页，下一页 # max_id # min_id 下一页： select * from userinfo3 where id > max_id limit 10; 上一页： select * from userinfo3 where id < min_id order by id desc limit 10; 2. 上一页 192 193 [196] 197 198 199 下一页 select * from userinfo3 where id in ( select id from (select id from userinfo3 where id > max_id limit 30) as N order by N.id desc limit 10 ) c. 数据库的id不连续： id不连续，所以无法直接使用id范围进行查找
from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index,CHAR,VARCHAR from sqlalchemy.orm import sessionmaker, relationship from sqlalchemy import create_engine # import pymysql Base = declarative_base() class UserType(Base): __tablename__ = 'usertype' id = Column(Integer, primary_key=True, autoincrement=True) title = Column(VARCHAR(32), nullable=True, index=True) class Users(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True, autoincrement=True) name = Column(VARCHAR(32), nullable=True, index=True) email = Column(VARCHAR(16), unique=True) user_type_id = Column(Integer,ForeignKey("usertype.id")) # user_type = relationship("UserType",backref='xxoo') # def create_db(): engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/shang?charset=utf8", max_overflow=5) Base.metadata.create_all(engine) # engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/shang?charset=utf8", max_overflow=5) # Session = sessionmaker(bind=engine) # session = Session() # # session.commit() # session.close()
from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index,CHAR,VARCHAR from sqlalchemy.orm import sessionmaker, relationship from sqlalchemy import create_engine # import pymysql Base = declarative_base() class UserType(Base): __tablename__ = 'usertype' id = Column(Integer, primary_key=True, autoincrement=True) title = Column(VARCHAR(32), nullable=True, index=True) class Users(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True, autoincrement=True) name = Column(VARCHAR(32), nullable=True, index=True) email = Column(VARCHAR(16), unique=True) user_type_id = Column(Integer,ForeignKey("usertype.id")) # user_type = relationship("UserType",backref='xxoo') def create_db(): engine = create_engine("mysql+pymysql://root:shang123@127.0.0.1:3306/chun?charset=utf8", max_overflow=5) Base.metadata.create_all(engine) def drop_db(): engine = create_engine("mysql+pymysql://root:shang123@127.0.0.1:3306/shang?charset=utf8", max_overflow=5) Base.metadata.drop_all(engine) # create_db() engine = create_engine("mysql+pymysql://root:shang123@127.0.0.1:3306/shang?charset=utf8", max_overflow=5) Session = sessionmaker(bind=engine) session = Session() # objs = [UserType(title='上是开放的接口'),UserType(title='shang2'),UserType(title='shang3'),UserType(title='shang4')] # session.add_all(objs) # print(session.query(UserType)) # user_type_list = session.query(UserType.id,UserType.title).filter(UserType.id>5) # for i in user_type_list: # print(i.id,i.title) # print(user_type_list,type(user_type_list)) # session.query(UserType.id,UserType.title).filter(UserType.id>5).delete() # session.query(UserType.id,UserType.title).filter(UserType.id>3).update({'title':'chun'}) # session.query(UserType.id,UserType.title).filter(UserType.id>3).update({UserType.title:UserType.title +'ss'},synchronize_session=False) session.commit() session.close()
from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index,CHAR,VARCHAR from sqlalchemy.orm import sessionmaker, relationship from sqlalchemy import create_engine Base = declarative_base() # 创建单表 """ 1 白金 2 黑金 obj.xx ==> [obj,obj...] """ class UserType(Base): __tablename__ = 'usertype' id = Column(Integer, primary_key=True, autoincrement=True) title = Column(VARCHAR(32), nullable=True, index=True) """ 1 方少伟 1 2 成套 1 3 小白 2 # 正向 ut = relationship（backref='xx'） obj.ut ==> 1 白金 """ class Users(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True, autoincrement=True) name = Column(VARCHAR(32), nullable=True, index=True) email = Column(VARCHAR(16), unique=True) user_type_id = Column(Integer,ForeignKey("usertype.id")) user_type = relationship("UserType",backref='xxoo') # __table_args__ = ( # UniqueConstraint('id', 'name', name='uix_id_name'), # Index('ix_n_ex','name', 'email',), # ) def create_db(): engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/s4day62db?charset=utf8", max_overflow=5) Base.metadata.create_all(engine) def drop_db(): engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/s4day62db?charset=utf8", max_overflow=5) Base.metadata.drop_all(engine) engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/s4day62db?charset=utf8", max_overflow=5) Session = sessionmaker(bind=engine) session = Session() # 类 -> 表 # 对象 -> 行 # ###### 增加 ###### # # obj1 = UserType(title='普通用户') # session.add(obj1) # objs =[ # UserType(title='超级用户'), # UserType(title='白金用户'), # UserType(title='黑金用户'), # ] # session.add_all(objs) # ###### 查 ###### # print(session.query(UserType)) # user_type_list = session.query(UserType).all() # for row in user_type_list: # print(row.id,row.title) # select xxx UserType where # user_type_list = session.query(UserType.id,UserType.title).filter(UserType.id > 2) # for row in user_type_list: # print(row.id,row.title) # 分组，排序，连表，通配符，子查询，limit，union,where,原生SQL、 # ret = session.query(Users, UserType) # select * from user,usertype; # # ret = session.query(Users, UserType).filter(Users.usertype_id==UserType.id) # select * from user,usertype whre user.usertype_id = usertype.id # result = session.query(Users).join(UserType) # print(result) # result = session.query(Users).join(UserType,isouter=True) # print(result) # # 1. # select * from b where id in (select id from tb2) # 2 select * from (select * from tb) as B # q1 = session.query(UserType).filter(UserType.id > 0).subquery() # result = session.query(q1).all() # print(result) # 3 # select # id , # (select * from users where users.user_type_id=usertype.id) # from usertype; # session.query(UserType,session.query(Users).filter(Users.id == 1).subquery()) # session.query(UserType,Users) # result = session.query(UserType.id,session.query(Users).as_scalar()) # print(result) # result = session.query(UserType.id,session.query(Users).filter(Users.user_type_id==UserType.id).as_scalar()) # print(result) # 问题1. 获取用户信息以及与其关联的用户类型名称(FK,Relationship=>正向操作) # user_list = session.query(Users,UserType).join(UserType,isouter=True) # print(user_list) # for row in user_list: # print(row[0].id,row[0].name,row[0].email,row[0].user_type_id,row[1].title) # user_list = session.query(Users.name,UserType.title).join(UserType,isouter=True).all() # for row in user_list: # print(row[0],row[1],row.name,row.title) # user_list = session.query(Users) # for row in user_list: # print(row.name,row.id,row.user_type.title) # 问题2. 获取用户类型 # type_list = session.query(UserType) # for row in type_list: # print(row.id,row.title,session.query(Users).filter(Users.user_type_id == row.id).all()) # type_list = session.query(UserType) # for row in type_list: # print(row.id,row.title,row.xxoo) # ###### 删除 ###### # session.query(UserType.id,UserType.title).filter(UserType.id > 2).delete() # ###### 修改 ###### # session.query(UserType.id,UserType.title).filter(UserType.id > 0).update({"title" : "黑金"}) # session.query(UserType.id,UserType.title).filter(UserType.id > 0).update({UserType.title: UserType.title + "x"}, synchronize_session=False) # session.query(UserType.id,UserType.title).filter(UserType.id > 0).update({"num": Users.num + 1}, synchronize_session="evaluate") session.commit() session.close()
1. 函数编程：数据和逻辑分离 a= 123 b = 456 c = 789 def exc3(proc_name): callproc(xxx) return xxx def exc4(proc_name): callproc(xxx) return xxx 2. 面向对象：数据和逻辑（属性和行为）组合在一起 class SqlHelper: def __init__(self): self.host = '' self.port ='' self.db ='' self.charset='' def exc1(self,SQL): # 连接 conn(self.host,) execute("inser") return xx def exc2(self,proc_name): callproc(xxx) return xxx - 一类事物共同具有：属性和行为 class Person: def __init__(self,name): self.name = name def speak(self): pass 1. 提取共性 2. 分类 3. 模板“约束” 4. 当一类函数公用同样参数时候，可以转变成类进行 - 分类 3. 面向对象： 数据和逻辑（属性和行为）组合在一起 函数编程：数据和逻辑分离 3. 分类示例： 类 = 表；对象=行 class Userinfo: def __init__(self,id,name): """ ‘约束’每个对象中只有两个字段，即：每个行数据都有id和name列""" self.id = id self.name= name def add(self,name): pass ... # row1 = UserInfo(1,'alex') # 第一行 # row2 = UserInfo(2,'alex') # 第二行 特殊方法： class Foo: def __init__(self,name): self.name = name def show(self): print(self.name) def __call__(self): pass def __getitem__(self,key): pass def __setitem__(self,key,value): pass def __delitem__(self,key): pass obj1 = Foo('eric') obj1() obj1['k'] obj1['k'] = 123 del obj[k] obj.__dict__ 1. ORM框架：SQLAlchemy - 作用： 1. 提供简单的规则 2. 自动转换成SQL语句 - DB first: 手动创建数据库以及表 -> ORM框架 -> 自动生成类 - code first： 手动创建类、和数据库 -> ORM框架 -> 以及表 a. 功能 - 创建数据库表 - 连接数据库（非SQLAlchemy,pymyql,mysqldb,....） - 类转换SQL语句 - 操作数据行 增 删 改 查 - 便利的功能 2. 自己开发Web框架 - socket - http协议 - HTML知识 - 数据库（pymysql，SQLAlchemy）