( db_url, max_overflow=0, pool_size=16, pool_timeout=5, pool_recycle=-1 ) if not database_exists(engine.url): create_database(engine.url) return False else: return True def init_database(db_url: str): # 设置连接池的大小 engine = create_engine( db_url, max_overflow=0, # ...
drop database 数据库名 (3)判断数据库是否存在 1>sysdatabases表:保存在master数据库中,这张表保存了所有数据库的信息 sysobjects表:数据库的系统表 例: 判断数据库是否存在,如果存在输出a,否则输出b if(exists(select * from sysdatabases where name='students')) begin select 'a' end else begin select ...
Integer from sqlalchemy.ext.declarative import declarative_base #导入相应的模块 engine = create_engine("mysql+pymysql://mysql:123456@10.0.0.8:3306/test", max_overflow=5) #创建数据库连接,max_overflow指定最大连接
问Flask-SQLAlchemy检查数据库中是否存在表EN1. 判断数据库是否存在 case mnesia:system_info(use_dir...
>>> s.query(A).filter(A.b_values.contains("hi")).all() SELECT a.id AS a_id FROM a WHERE EXISTS (SELECT 1 FROM atob WHERE a.id = atob.a_id AND (EXISTS (SELECT 1 FROM b WHERE b.id = atob.b_id AND b.value = :value_1))) 类似地,我们可以使用AssociationProxy.any()在A...
fromsqlalchemyimportcreate_enginefromsqlalchemy.ext.declarativeimportdeclarative_basefromsqlalchemy.ormimportsessionmaker# 创建数据库引擎DATABASE_URL="postgresql://user:password@localhost/dbname"engine=create_engine(DATABASE_URL,echo=True,# 设置为True可打印SQL语句,开发环境有用pool_size=5,# 连接池大小...
5. Delete Data from the Database This example demonstrates how to delete a record. Code: # Fetch a user by ID user_to_delete = session.query(User).filter_by(id=1).first() # Get the user with ID 1 if user_to_delete: # Check if the user exists ...
DATABASE_CONFIG = { "username":"root", "password":"123456", "host":"localhost", "database":"test" } # 连接mysql engine = create_engine("mysql+pymysql://{username}:{password}@{host}/{database}".format(**DATABASE_CONFIG),
# will check if enum exists, and emit CREATE TYPE if not t1.create(engine, checkfirst=True) 当使用基于元数据的 ENUM 类型时,如果调用元数据范围的创建/删除,则该类型将始终被创建和删除: metadata.create_all(engine) # will emit CREATE TYPE metadata.drop_all(engine) # will emit DROP TYPE ...
class CheckUsername(Resource): def get(self, un): un = un.lower() existing_user = User.query.filter_by(un=un).first() if existing_user: return {'error': '用户名已存在。'}, 400 return {'message': '该用户名可用。'}, 200