sql - 列出一个表的所有外键，同一个表的多个外键

Question

我使用以下 SQL 查询给定表的键(主键和外键)及其描述。我正在使用 SQL Server 2005。

SELECT  c.name 'Column Name' ,
    t.name 'Data type' ,
    c.max_length 'Max Length' ,
    c.precision ,
    c.scale ,
    c.is_nullable ,
    ISNULL(i.is_primary_key, 0) 'Primary Key' ,
    CAST (( SELECT  COUNT(*)
            FROM    ( SELECT    cx.object_id
                      FROM      sys.foreign_key_columns fkc
                                INNER JOIN sys.columns cx ON fkc.parent_column_id = cx.column_id
                                                          AND fkc.parent_object_id = cx.object_id
                                INNER JOIN sys.columns cref ON fkc.referenced_column_id = cref.column_id
                                                          AND fkc.referenced_object_id = cref.object_id
                      WHERE     cx.column_id = c.column_id
                                AND fkc.parent_object_id = OBJECT_ID('[dbo].Cards')
                    ) xxx
          ) AS BIT) AS 'Foreign Key' ,
    ( SELECT    OBJECT_SCHEMA_NAME(fkc.referenced_object_id)
      FROM      sys.foreign_key_columns fkc
                INNER JOIN sys.columns cy ON fkc.parent_column_id = cy.column_id
                                             AND fkc.parent_object_id = cy.object_id
                INNER JOIN sys.columns cref ON fkc.referenced_column_id = cref.column_id
                                               AND fkc.referenced_object_id = cref.object_id
      WHERE     cy.column_id = c.column_id
                AND fkc.parent_object_id = OBJECT_ID('[dbo].Cards')
    ) 'Schema Name' ,
    ( SELECT    OBJECT_NAME(referenced_object_id)
      FROM      sys.foreign_key_columns fkc
                INNER JOIN sys.columns cy ON fkc.parent_column_id = cy.column_id
                                             AND fkc.parent_object_id = cy.object_id
                INNER JOIN sys.columns cref ON fkc.referenced_column_id = cref.column_id
                                               AND fkc.referenced_object_id = cref.object_id
      WHERE     cy.column_id = c.column_id
                AND fkc.parent_object_id = OBJECT_ID('[dbo].Cards')
    ) 'Referenced table' ,
    ( SELECT    cref.name
      FROM      sys.foreign_key_columns fkc
                INNER JOIN sys.columns cy ON fkc.parent_column_id = cy.column_id
                                             AND fkc.parent_object_id = cy.object_id
                INNER JOIN sys.columns cref ON fkc.referenced_column_id = cref.column_id
                                               AND fkc.referenced_object_id = cref.object_id
      WHERE     cy.column_id = c.column_id
                AND fkc.parent_object_id = OBJECT_ID('[dbo].Cards')
    ) 'Referenced column name' ,
    ( SELECT    sep.value [Description]
      FROM      sys.extended_properties sep
      WHERE     OBJECT_ID('[dbo].Cards') = sep.major_id
                AND c.column_id = sep.minor_id
    ) Description FROM sys.columns c
    INNER JOIN sys.types t ON c.user_type_id = t.user_type_id
    LEFT OUTER JOIN sys.index_columns ic ON ic.object_id = c.object_id
                                            AND ic.column_id = c.column_id
    LEFT OUTER JOIN sys.indexes i ON ic.object_id = i.object_id
                                     AND ic.index_id = i.index_id WHERE   c.object_id = OBJECT_ID('[dbo].Cards');

该查询适用于所有表，除非该表有两个指向同一个表的外键。

我得到的错误是，

"Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression."

我做错了什么？

Answer 1

我没有检查你的第二个查询，但问题仍然存在:返回超过1个值的子查询是这个

( SELECT    sep.value [Description]
  FROM      sys.extended_properties sep
  WHERE     OBJECT_ID('person.stateProvince') = sep.major_id
            AND c.column_id = sep.minor_id                 
) Description 

您应该在 where 子句中添加附加条件:

and class = 1 -- OBJECT_OR_COLUMN

您的查询不考虑表的超过 1 个索引，加入 c.column_id = sep.minor_id 您可以获得更多行，因为当类为 7(索引)时 minor_id 是索引 ID，而不是列 ID