{"componentChunkName":"component---src-templates-blog-post-js","path":"/sqlalchemy/2020-08-03-SQLAlchemy-CRUD/","result":{"data":{"site":{"siteMetadata":{"title":"Jinote","author":"jinoan","siteUrl":"https://jinoan.netlify.app","comment":{"disqusShortName":"","utterances":"jinoan/blog-comment"},"sponsor":{"buyMeACoffeeId":"jinoan"}}},"markdownRemark":{"id":"9d4e3760-6297-5533-bde3-1f41333378ca","excerpt":"models.py 만들기 SQLAlchemy로 DB를 사용하기 위해 DB의 테이블 객체를 생성해야 한다.\nflask-sqlacodegen으로 쉽게 생성 가능. flask-sqlacodegen 설치 models.py 생성 (PostgreSQL 사용시) 테이블 객체의 형태 Session 연결 CRUD Select Insert Update Delete 그 외… Join Pandas data frame으로 결과 불러오기","html":"

models.py 만들기

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SQLAlchemy로 DB를 사용하기 위해 DB의 테이블 객체를 생성해야 한다.\nflask-sqlacodegen으로 쉽게 생성 가능.

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flask-sqlacodegen 설치

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$ pip3 install flask-sqlacodegen
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models.py 생성 (PostgreSQL 사용시)

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$ flask-sqlacodegen \"postgresql://{아이디}:{패스워드}@{DB호스트}:{포트번호}/{DB이름}\" --flask > models.py
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테이블 객체의 형태

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class Table(db.Model):\n    __tablename__ = 'tables'\n\n    table_pkey = db.Column(db.Integer, primary_key=True, server_default=db.FetchedValue())\n    tname = db.Column(db.String(10), nullable=False)\n    tmaker = db.Column(db.ForeignKey('makers.mname', ondelete='CASCADE'))\n\n    maker = db.relationship('Maker', primaryjoin='Table.tmaker == Maker.mname', backref='tables')
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Session 연결

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import models  # models.py\nfrom sqlalchemy import create_engine\nfrom sqlalchemy.orm import sessionmaker\n\nengine = create_engine('postgresql://{아이디}:{패스워드}@{DB호스트}:{포트번호}/{DB이름}')\nSession = sessionmaker(bind=engine)\nsession = Session()
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CRUD

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Select

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# select * from tables;\nres_all = session.query(models.Table).all()\nfor rec in res_all:\n    print(f'tname: {rec.tname}, tmaker: {rec.tmaker}')\n\n# select * from tables where tname = 'aaa';\nres_aaa = session.query(models.Table).filter_by(tname='aaa').first()\n# .filter()를 사용해도 됨\nres_aaa = session.query(models.Table).filter(models.Table.tname == 'aaa').first()\nprint(res_aaa.tmaker)
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Insert

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# insert into tables(tname, tmaker) values ('bbb', 'jinoan');\ndata = models.Table(tname='bbb', tmaker='jinoan')\nsession.add(data)\nsession.commit()
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Update

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# update tables set tname = 'ccc' where tname = 'bbb';\nres_bbb = session.query(models.Table).filter_by(tname='bbb').first()\nres_bbb.tname = 'ccc'\nsession.commit()
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Delete

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# delete from tables where tname = 'ccc';\nsession.query(models.Table).filter_by(tname='ccc').delete()\n\n# commit하지 않고 되돌리고 싶을 때\nsession.rollback()\n\n# delete를 다음처럼 할 수도 있다.\nres_ccc = session.query(models.Table).filter_by(tname='ccc').first()\nsession.delete(res_ccc)\n\nsession.commit()
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그 외…

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Join

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res_all = session.query(models.Table).join(models.Maker).all()\n\n# reference 값이 무엇인지 정확히 명시하려면\nres_all = session.query(models.Table)\\\n\t.select_from(models.Table)\\\n    .join(models.Maker, models.Table.tmaker==models.Maker.mname).all()
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Pandas data frame으로 결과 불러오기

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import pandas as pd\n\nquery = session.query(models.Table)\ndf = pd.read_sql(query.statement, session.bind)\nprint(df)
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