将 SQL 转换为 SQL 炼金术

2021-12-30 00:00:00 python sqlalchemy flask-sqlalchemy orm mysql

我是 Flask SQl 炼金术的新手；虽然我知道炼金术抽象了 sql 语法并在创建模型时使事情变得容易；有时我们希望以非常具体的方式在前端可视化数据.

I am new to Flask SQl alchemy; Though i understand that alchemy abstracts the sql syntax and makes things easy while creating models; there could be times when we want to visualize data in the front end in a very specific way.

我有以下查询，我想使用 alchemy 使用 session.query 和过滤器以及可能的分组.

I have the following query which i would like to use using alchemy using session.query and filter and possibly grouping.

我的查询内容如下:

  1. mysql> SELECT status, COUNT(id) FROM bar_baz where not name = 'Foo' and not name = 'Bar' GROUP BY status
  2. select (select COUNT(id) FROM instance where not name = 'erf' and not tiername = 'wer' and type='app') as app, (select COUNT(1) FROM instance_2 where not name= 'visq' 而不是 name = 'werf' and type='adc') as adc from dual;

我确认以下查询适用于 MySQL；我想知道我们是否有类似于

I verified that the following queries works with the MySQL; I was wondering if we have a function similar to

c = conn.cursor()
query = 'SELECT status, COUNT(id) FROM bar_baz where not name = 'Foo' and not name = 'Bar' GROUP BY status'
c.execute(query)
print c.fetchall()


class Instance(Base):
    __tablename__ = 'instance'

    id = Column(Integer, primary_key=True)
    name = Column(String)
    status = Column(String)
    type = Column(String)

class Instance2(Base):
    __tablename__ = 'instance_2'

    id = Column(Integer, primary_key=True)
    name = Column(String)
    status = Column(String)
    type = Column(String)
    inc = Column(Integer)

兴趣查询:

select (select COUNT(id) FROM instance where not name = 'erf' and not tiername = 'wer' and type='app') as app, (select COUNT(1) FROM instance_2 where not name = 'visq' and not name = 'werf' and type='adc') as adc from dual;`

推荐答案

对于第一个查询，使用 db.func.count 生成计数表达式.从 docs 中可以看出其他所有内容.

For the first query, use db.func.count to produce the count expression. Everything else should be obvious from the docs.

status_counts = db.session.query(BarBaz.status, db.func.count(BarBaz.id).label('count_id')
).filter(db.not_(db.or_(BarBaz.name == 'Foo', BarBaz.name == 'Bar'))
).group_by(BarBaz.status
).all()

对于第二个查询，使用 subquery() 生成可选择的查询.

For the second query, use subquery() to produce selectable queries.

sub_app = db.session.query(db.func.count(Instance.id).label('app')
).filter(db.not_(db.or_(Instance.name == 'erf', Instance.tiername == 'wer')), Instance.type == 'app'
).subquery()

sub_adc = db.session.query(db.func.count(Instance.id).label('adc')
).filter(db.not_(db.or_(Instance2.name == 'visq', Instance2.name == 'werf')), Instance2.type == 'adc'
).subquery()

out = db.session.query(sub_app.c.app, sub_adc.c.adc).all()

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