Flask-Sqlalchemy：具有 3 个主键也是外键的表

Question

我正在尝试将表从纯 SQL 转换为 Flask-Sqlalchemy，但是可用的文档并不清楚如何执行此特定场景 - 主键也是外键。

构建表的 SQL 如下所示，它工作正常：

CREATE TABLE IF NOT EXISTS `ws`.`Perfil_Plano_Transacao` (
    `pptr_perf_id` INT NOT NULL,
    `pptr_tran_id` INT NOT NULL,
    `pptr_plan_id` INT NOT NULL,
    `pptr_dt_incluscao` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    `pptr_dt_atualizacao` TIMESTAMP NULL,
PRIMARY KEY (`pptr_perf_id`, `pptr_tran_id`, `pptr_plan_id`),
INDEX `fk_Perfil_Plano_Transacao_Transacao1_idx` (`pptr_tran_id` ASC),
INDEX `fk_Perfil_Plano_Transacao_Plano1_idx` (`pptr_plan_id` ASC),
CONSTRAINT `fk_Perfil_Plano_Transacao_Perfil1`
    FOREIGN KEY (`pptr_perf_id`)
    REFERENCES `ws`.`Perfil` (`perf_id`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
CONSTRAINT `fk_Perfil_Plano_Transacao_Transacao1`
    FOREIGN KEY (`pptr_tran_id`)
    REFERENCES `ws`.`Transacao` (`tran_id`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
CONSTRAINT `fk_Perfil_Plano_Transacao_Plano1`
    FOREIGN KEY (`pptr_plan_id`)
    REFERENCES `ws`.`Plano` (`plan_id`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB

我到这里来的 Python 代码是：

class PerfilPlanoTransacaoModel(db.Model):

    __tablename__ = 'perfil_plano_transacao'

    pptr_perf_id = db.Column(db.Integer, primary_key=True, autoincrement=False)
    pptr_plan_id = db.Column(db.Integer, primary_key=True, autoincrement=False)
    pptr_tran_id = db.Column(db.Integer, primary_key=True, autoincrement=False)
    pptr_dt_inclusao = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
    pptr_dt_atualizacao = db.Column(db.DateTime, nullable=True)

    __table_args__ = (
        db.ForeignKeyConstraint(
            ['pptr_perf_id', 'pptr_plan_id', 'pptr_tran_id'],
            ['perfil.perf_id', 'plano.plan_id', 'transacao.tran_id'],
            ['fk_Perfil_Plano_Transacao_Perfil1', 'fk_Perfil_Plano_Transacao_Plano1', 'fk_Perfil_Plano_Transacao_Transacao1']
        ),
    )

我想知道我是否朝着正确的方向前进。例如，我没有找到如何声明name外键约束以及如何设置INDEX. 有没有更多的Flaks-Sqlalchemy方法可以做到这一切？

Answer 1

@Halvor 的答案是正确的，但我只想补充一点，您有一个复合主键而不是复合外键，您有三个单列外键指向不同的表，这意味着您可以在列中声明外键定义也是：

from sqlalchemy import ForeignKey

class PerfilPlanoTransacaoModel(db.Model):

    __tablename__ = 'perfil_plano_transacao'

    pptr_perf_id = db.Column(
        db.Integer, 
        ForeignKey('perfil.perf_id'),
        primary_key=True, 
        autoincrement=False,
    )
    pptr_plan_id = db.Column(
        db.Integer, 
        ForeignKey('plano.plan_id'),
        primary_key=True, 
        autoincrement=False,
    )
    pptr_tran_id = db.Column(
        db.Integer, 
        ForeignKey('transacao.tran_id'),
        primary_key=True, 
        autoincrement=False,
    )
    pptr_dt_inclusao = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
    pptr_dt_atualizacao = db.Column(db.DateTime, nullable=True)

UsingForeignKeyConstraint比 using 更冗长，ForeignKey并且ForeignKey我们在此示例中的列定义中创建的对象最终ForeignKeyConstraint无论如何都会转换为对象，只是ForeignKey在处理单列键时使用对象更容易。中ForeignKeyConstraint定义的对象__table_args__通常仅在需要创建复合外键时直接使用，例如，如果您有另一个要引用的表perfil_plano_transacao，则它需要是复合外键，并且您必须像您一样定义它上面已经做了。

对于您的其余问题，我将遵循@Halvor 的回答。