由于双主键无法映射ForeignKey

Question

我试图从现有数据实时创建表...但是，我需要的表有双主键。我无法找到如何满足限制。

I.e.我先从下面两个表...

self.DDB_PAT_BASE = Table('DDB_PAT_BASE', METADATA, 
    Column('PATID', INTEGER(), primary_key=True), 
    Column('PATDB', INTEGER(), primary_key=True), 
    Column('FAMILYID', INTEGER()), 
) 

self.DDB_ERX_MEDICATION_BASE = Table('DDB_ERX_MEDICATION_BASE', METADATA, 
    Column('ErxID', INTEGER(), primary_key=True), 
    Column('ErxGuid', VARCHAR(length=36)), 
    Column('LastDownload', DATETIME()), 
    Column('LastUpload', DATETIME()), 
    Column('Source', INTEGER()), 
    ) 

当我尝试以下方法，它的工作原理...

t = Table('testtable', METADATA, 
    Column('ErxID', INTEGER(), ForeignKey('DDB_ERX_MEDICATION_BASE.ErxID')), 
    )  
t.create() 

但是，下面的两个给我的错误...

t = Table('testtable', METADATA, 
    Column('PATID', INTEGER(), ForeignKey('DDB_PAT_BASE.PATID')), 
) 
t.create() 

t = Table('testtable', METADATA, 
    Column('PATID', INTEGER(), ForeignKey('DDB_PAT_BASE.PATID')), 
    Column('PATDB', INTEGER(), ForeignKey('DDB_PAT_BASE.PATDB')), 
) 
t.create() 

sqlalchemy.exc.OperationalError: (pymssql.OperationalError) (1776, "There are no primary or candidate keys in the referenced table 'DDB_PAT_BASE' that match the referencing column list in the foreign key 'FK__testtabl__PATID__3FD3A585'.DB-Lib error message 20018, severity 16:\nGeneral SQL Server error: Check messages from the SQL Server\nDB-Lib error message 20018, severity 16:\nGeneral SQL Server error: Check messages from the SQL Server\n") [SQL: '\nCREATE TABLE [testtable] (\n\t[PATID] INTEGER NULL, \n\tFOREIGN KEY([PATID]) REFERENCES [DDB_PAT_BASE] ([PATID])\n)\n\n'] 

Answer 1

您指向的表有一个复合主键，而不是多个主键。因此。你需要创建一个复合外键，而不是指向复合主键的每一半的两个外键：

t = Table('testtable', METADATA, 
    Column('PATID', INTEGER()), 
    Column('PATDB', INTEGER()), 
    ForeignKeyConstraint(['PATID', 'PATDB'], ['DDB_PAT_BASE.PATID', 'DDB_PAT_BASE.PATDB']), 
) 
t.create()