使用SQL服務器中的外鍵自動加入表，pyodbc

Question

我使用python訪問SQL服務器的數據庫。該數據庫有大約200個表，並且它包含表之間的外鍵。

我想使用數據庫中的外鍵自動連接表，因爲手動操作非常繁瑣。

如何使用給定的外鍵創建所有表的所有最大可能連接的熊貓數據框？

隨着pyodbc，我能順利拿到每一個具體的表格製作這一行代碼連接後：

cnxn = pyodbc.connect("...") 

Answer 1

這不是SQL的標準功能。您將不得不查詢系統架構表中的關係&，然後自己構建查詢，可能使用左連接。 我目前正在嘗試類似的東西，這裏是我用來從SQL Server獲取關係的SQL。

with fKC as 
(
    select 
      sfkc.constraint_object_id 
      ,(select name from sys.objects as o where o.object_id=sfkc.constraint_object_id) as constraint_object_name 
      ,sfkc.parent_object_id 
      ,(select name from sys.objects as o where o.object_id=sfkc.parent_object_id) as parent_object_name 
      ,sfkc.parent_column_id 
      ,(select name from sys.columns as c where ((c.object_id=sfkc.parent_object_id)and(c.column_id=sfkc.parent_column_id))) as parent_column_name 
      ,sfkc.referenced_object_id 
      ,(select name from sys.objects as o where o.object_id=sfkc.referenced_object_id) as referenced_object_name 
      ,sfkc.referenced_column_id 
      ,(select name from sys.columns as c where ((c.object_id=sfkc.referenced_object_id)and(c.column_id=sfkc.referenced_column_id))) as referenced_column_name 
    from sys.foreign_key_columns as sfkc 
    where (sfkc.parent_object_id!=sfkc.referenced_object_id) 
) 

select * 
from fKC 
order by fKC.parent_object_name, fKC.referenced_object_name;