Flask-Sqlalchemy：Table 有 3 个主键也是外键

Question

我正在尝试将 table 从纯 SQL 转换为 Flask-Sqlalchemy，但可用的文档不清楚如何执行此特定场景 - 主键也是外键.

构建 table 的 SQL 如下，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

我到这里为止的 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']
        ),
    )

我想知道我走的路是否正确。例如，我没有找到如何声明外键约束的 name 以及如何设置 INDEX。是否有更多 Flaks-Sqlalchemy 方法来完成这一切？

Answer 1

如何声明name外键约束

添加多个外键约束可以通过在 __table_args__ 中设置多个 ForeignKeyConstraint 来完成。例如：

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

在这里您可以看到您定义了本地列，然后是原始 table 中的列并为其命名。前两个参数是数组的原因是允许复合外键。

对您的代码进行此更改应评估以下查询：

CREATE TABLE perfil_plano_transacao (
        pptr_perf_id INTEGER NOT NULL,
        pptr_plan_id INTEGER NOT NULL,
        pptr_tran_id INTEGER NOT NULL,
        pptr_dt_inclusao DATETIME NOT NULL,
        pptr_dt_atualizacao DATETIME,
        PRIMARY KEY (pptr_perf_id, pptr_plan_id, pptr_tran_id),
        CONSTRAINT "fk_Perfil_Plano_Transacao_Perfil1" FOREIGN KEY(pptr_perf_id) REFERENCES perfil (perf_id),
        CONSTRAINT "fk_Perfil_Plano_Transacao_Plano1" FOREIGN KEY(pptr_plan_id) REFERENCES plano (plan_id),
        CONSTRAINT "fk_Perfil_Plano_Transacao_Transacao1" FOREIGN KEY(pptr_tran_id) REFERENCES transacao (tran_id)
)

如何设置INDEX

添加索引的简单方法是在列声明中设置它：

pptr_perf_id = Column(Integer, primary_key=True, autoincrement=False)
pptr_plan_id = Column(Integer, primary_key=True, autoincrement=False, index=True)
pptr_tran_id = Column(Integer, primary_key=True, autoincrement=False, index=True)

这将导致以下两个查询：

CREATE INDEX ix_perfil_plano_transacao_pptr_plan_id ON perfil_plano_transacao (pptr_plan_id)
CREATE INDEX ix_perfil_plano_transacao_pptr_tran_id ON perfil_plano_transacao (pptr_tran_id)

或者在table声明后单独添加：

from sqlalchemy import Index
Index('fk_Perfil_Plano_Transacao_Transacao1_idx', PerfilPlanoTransacaoModel.pptr_tran_id.asc())
Index('fk_Perfil_Plano_Transacao_Plano1_idx', PerfilPlanoTransacaoModel.pptr_plan_id.asc())

这将导致以下两个查询：

CREATE INDEX "fk_Perfil_Plano_Transacao_Transacao1_idx" ON perfil_plano_transacao (pptr_tran_id ASC)
CREATE INDEX "fk_Perfil_Plano_Transacao_Plano1_idx" ON perfil_plano_transacao (pptr_plan_id ASC)

Answer 2

@Halvor 的回答是正确的，但我要补充一点，你有一个复合主键但没有复合外键，你有三个单列外键指向不同的 tables意味着您也可以在列定义中声明外键：

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)

使用 ForeignKeyConstraint 比使用 ForeignKey 稍微冗长一点，我们在此示例中的列定义中创建的 ForeignKey 对象最终会转换为 ForeignKeyConstraint对象，在处理单列键时使用 ForeignKey 对象更容易。 __table_args__ 中定义的 ForeignKeyConstraint 对象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 table 想要引用 perfil_plano_transacao，它需要是一个复合外键，您必须像上面那样定义它。

我将推迟@Halvor 对你问题的其余部分的回答。

Flask-Sqlalchemy：Table 有 3 个主键也是外键

Flask-Sqlalchemy: Table with 3 primary keys that are also foreign keys

python

sqlalchemy

foreign-keys

composite-primary-key

flask-sqlalchemy