Question

我需要使用sqlalchemy在mysql中创建一个db，如果它已经存在，我可以连接到db，但是如果它不存在我希望能够创建它。这是我的表：

    #def __init__(self):
Base = declarative_base()

class utente(Base):
    __tablename__="utente"
    utente_id=Column(Integer,primary_key=True)
    nome_utente=Column(Unicode(20))
    ruolo=Column(String(10))
    MetaData.create_all()

    def __repr(self):
        return "utente: {0}, {1}, id: {2}".format(self.ruolo,self.nome_utente,self.utente_id)


class dbmmas(Base):

    __tablename__="dbmmas"
    db_id=Column(Integer,primary_key=True,autoincrement=True)
    nome_db=Column(String(10))
    censimento=Column(Integer)
    versione=Column(Integer)
    ins_data=Column(DateTime)
    mod_data=Column(DateTime)
    ins_utente=Column(Integer)
    mod_utente=Column(Integer)
    MetaData.create_all()

    def __repr(self):
        return "dbmmas: {0}, censimento {1}, versione {2}".format(self.nome_db,self.censimento,self.versione)    

class funzione(Base):
    __tablename__="funzione"
    funzione_id=Column(Integer,primary_key=True,autoincrement=True)
    categoria=Column(String(10))
    nome=Column(String(20))
    def __repr__(self):
        return "funzione:{0},categoria:{1},id:{2} ".format(self.nome,self.categoria,self.funzione_id)

class profilo(Base):
    __tablename__="rel_utente_funzione" 
    utente_id=Column(Integer,primary_key=True)
    funzione_id=Column(Integer,primary_key=True)
    amministratore=Column(Integer)
    MetaData.create_all()

    def __repr(self):
        l=lambda x: "amministratore" if x==1 else "generico"
        return "profilo per utente_id:{0}, tipo: {1}, funzione_id: {2}".format(self.utente_id,l(self.amministratore),self.funzione_id)    

class aree(Base):
    __tablename__="rel_utente_zona"
    UTB_id=Column(String(10), primary_key=True) # "in realta' si tratta della seatureSignature della feature sullo shapefile"
    utente_id=Column(Integer, primary_key=True)
    amministratore=Column(Integer)
    MetaData.create_all()
    def __repr(self):
        l=lambda x: "amministratore" if x==1 else "generico"
        return "zona: {0}, pe utente_id:{1}, {2}".format(self.UTB_id,self.utente_id,l(self.amministratore))

class rel_utente_dbmmas(Base):
    __tablename__="rel_utente_dbmmas"
    utente_id=Column(Integer,primary_key=True)
    db_id=Column(Integer,primary_key=True)
    amministratore=(Integer)
    MetaData.create_all()
    def __repr(self):
        l=lambda x: "amministratore" if x==1 else "generico"
        return "dbregistrato: {0} per l'utente{1} {2}".format(self.db_id,self.utente_id,l(self.amministratore))

Answer 1

要创建mysql数据库，只需连接到服务器即可创建数据库：

import sqlalchemy
engine = sqlalchemy.create_engine('mysql://user:password@server') # connect to server
engine.execute("CREATE DATABASE dbname") #create db
engine.execute("USE dbname") # select new db
# use the new db
# continue with your work...

当然，您的用户必须拥有创建数据库的权限。

Answer 2

CREATE DATABASE IF NOT EXISTS dbName;

Answer 3

您可以使用SQLAlchemy-Utils。

pip install sqlalchemy-utils

然后您可以做类似的事情

from sqlalchemy_utils import create_database, database_exists
url = 'mysql://{0}:{1}@{2}:{3}'.format(user, pass, host, port)
if not database_exists(url):
    create_database(url)

我找到了答案here，对我有很大帮助。

Answer 4

我不知道规范的方式是什么，但是这里有一种方法可以通过检查数据库列表来检查数据库是否存在，如果数据库不存在则创建数据库。

from sqlalchemy import create_engine

# This engine just used to query for list of databases
mysql_engine = create_engine('mysql://{0}:{1}@{2}:{3}'.format(user, pass, host, port))

# Query for existing databases
existing_databases = mysql_engine.execute("SHOW DATABASES;")
# Results are a list of single item tuples, so unpack each tuple
existing_databases = [d[0] for d in existing_databases]

# Create database if not exists
if database not in existing_databases:
    mysql_engine.execute("CREATE DATABASE {0}".format(database))
    print("Created database {0}".format(database))

# Go ahead and use this engine
db_engine = create_engine('mysql://{0}:{1}@{2}:{3}/{4}'.format(user, pass, host, port, db))

如果您不需要知道数据库是否已创建，则可以使用以下方法。

from sqlalchemy import create_engine

# This engine just used to query for list of databases
mysql_engine = create_engine('mysql://{0}:{1}@{2}:{3}'.format(user, pass, host, port))

# Query for existing databases
mysql_engine.execute("CREATE DATABASE IF NOT EXISTS {0} ".format(database))

# Go ahead and use this engine
db_engine = create_engine('mysql://{0}:{1}@{2}:{3}/{4}'.format(user, pass, host, port, db))

Answer 5

建议使用with：

from sqlalchemy import create_engine

username = ''
password = ''
host = 'localhost'
port = 3306
DB_NAME = 'db_name'

engine = create_engine(f"mysql://{username}:{password}@{host}:{port}")

with engine.connect() as conn:
    # Do not substitute user-supplied database names here.
    conn.execute(f"CREATE DATABASE IF NOT EXISTS {DB_NAME}")

如何使用sqlalchemy创建db mysql

5 个答案: