如何使用sqlalchemy创建db mysql

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,但是我希望能够创建它,如果它不存在的话.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,您的用户必须具有创建数据库的权限.

Answer 2

您可以为此使用SQLAlchemy-Utils。

pip install sqlalchemy-utils

然后你可以做类似的事情

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)

我在这里找到了答案，这对我有很大帮助。

Answer 3

CREATE DATABASE IF NOT EXISTS dbName;

Answer 4

我不知道规范的方法是什么，但是这是一种通过检查数据库列表来检查数据库是否存在的方法，如果不存在，则可以创建它。

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，则这是另一种方法。

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))