I'm new to flask, python and sql alchemy. I'm using flask for a small
application. Hence I'm using flask-sqlalchemy. I know it uses the
declarative base. I have model.py as:
from app import db
>
>
>>
>> def _create_db_sequence(name):
>
> # if db is Oracle create the sequence
>
> if db.engine.name.upper() == 'ORACLE':
>
> query = "SELECT * FROM user_sequences WHERE sequence_name =
>> '{}'".format(name)
>
> result = db.session.execute(query)
>
>
>> if not result.scalar():
>
> db.session.execute('CREATE SEQUENCE {}'.format(name))
>
> db.session.commit()
>
>
>>
>> class FieldType(db.Model):
>
> __tablename__ = 'field_types'
>
>
>> id = db.Column(db.Integer, db.Sequence('FIELD_TYPES_SEQ'),
>> primary_key=True)
>
> name = db.Column(db.String(120), unique=True, nullable=False) # a
>> nice name, like Date
>
>
>> # one-to-many relationship (many Fields can use the same FieldType)
>
> fields = db.relationship('Field', backref=db.backref('type',
>> lazy='joined'))
>
>
>> # python type for the field (int, double, str, date, etc)
>
> python_type = db.Column(db.String(120))
>
>
>> # for date will be 'from datetime import date as Date', for int, is
>> empty string
>
> python_import = db.Column(db.String(120))
>
>
>> _create_db_sequence('FIELD_TYPES_SEQ')
>
>
>>
>> class Field(db.Model):
>
> __tablename__ = 'fields'
>
>
>> id = db.Column(db.Integer, db.Sequence('FIELDS_SEQ'),
>> primary_key=True)
>
> name = db.Column(db.String(120), nullable=False)
>
> position = db.Column(db.Integer)
>
>
>> # a field has only one type
>
> type_id = db.Column(db.Integer, db.ForeignKey(FieldType.id))
>
>
>> # a field only belongs to one table
>
> table_info_id = db.Column(db.Integer, db.ForeignKey('tables_info.id'),
>> unique=True)
>
>
>> _create_db_sequence('FIELDS_SEQ')
>
>
>>
>> class TableInfo(db.Model):
>
> __tablename__ = 'tables_info'
>
>
>> id = db.Column(db.Integer, db.Sequence('TABLES_INFO_SEQ'),
>> primary_key=True)
>
> name = db.Column(db.String(120), unique=True, nullable=False)
>
>
>> # a table can have a lot of fields
>
> fields = db.relationship(Field, backref='table_info', lazy='joined')
>
>
>> # a table only belongs to one department
>
> department_id = db.Column(db.Integer, db.ForeignKey('departments.id'))
>
>
>> _create_db_sequence('TABLES_INFO_SEQ')
>
>
>>
>> class Department(db.Model):
>
> __tablename__ = 'departments'
>
>
>> id = db.Column(db.Integer, db.Sequence('DEPARTMENTS_SEQ'),
>> primary_key=True)
>
> name = db.Column(db.String(120), unique=True, nullable=False)
>
>
>> # one-to-many relationship (a Department can have several associated
>> TableInfos)
>
> tables_info = db.relationship(TableInfo,
>> backref=db.backref('department', lazy='joined'))
>
>
>> _create_db_sequence('DEPARTMENTS_SEQ')
>
> So I have a form that will collect the name attribute of TableInfo. Now,
> how do I dynamically - in runtime- create an empty table with the name
> attribute given? Once table is created, I will use another form to collect
> field/column names. Again, I'll like to dynamically add these columns to
> the table. Since this table and its columns won't be based on predefined
> models, how do I create the table and columns in runtime in a way that the
> application can interact with it? Can I create tables on the fly in a
> flask-sqlalchemy environment? Thanks.
>
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