Question

我在SQL Server上运行SQL查询，逻辑上应该返回一些数据，但它不会：

SELECT 
    D.NAME DATABASE_NAME, T.NAME TABLE_NAME, I.NAME INDEX_NAME,
    C.NAME COLUMN_NAME
FROM 
    sys.dm_db_index_physical_stats (NULL, NULL, NULL , NULL, 'LIMITED') AS XXX
INNER JOIN 
    SYS.DATABASES AS D ON D.DATABASE_ID = XXX.DATABASE_ID
INNER JOIN 
    SYS.TABLES AS T ON T.OBJECT_ID = XXX.OBJECT_ID
INNER JOIN 
    SYS.INDEXES AS I ON I.OBJECT_ID = T.OBJECT_ID
INNER JOIN 
    SYS.INDEX_COLUMNS IC ON IC.OBJECT_ID = I.OBJECT_ID
INNER JOIN 
    SYS.COLUMNS AS C ON C.OBJECT_ID = IC.OBJECT_ID
WHERE 
    1=1
ORDER BY 
    D.NAME, T.NAME

仅运行此位会输出大量数据：

SELECT * 
FROM sys.dm_db_index_physical_stats (NULL, NULL, NULL , NULL, 'LIMITED')

那么为什么更复杂的查询不起作用呢？

Answer 1

你没有正确地加入......

例如，index_columns有一个object_id（用于表）和一个index_id（用于索引）。请注意，indexid不是全局唯一的，而是仅在该表的上下文中唯一（即object_id），因此当您拉入index_columns时需要在两列上连接。

以下是一个例子：

SELECT 
    TOP 50 
      t.name as tablename, 
      i.name as indexname, 
      c.name as columnname, 
      ic.key_ordinal, ic.is_descending_key
FROM sys.tables t
INNER JOIN sys.indexes i
    ON i.object_id = t.object_id
INNER JOIN sys.columns c
    ON c.object_id = t.object_id
INNER JOIN sys.index_columns ic
    ON ic.object_id = t.object_id
    AND ic.index_id = i.index_id
    AND ic.column_id = c.column_id
ORDER by t.name, i.name, c.name, ic.key_ordinal

SQL Server：查询中没有应该返回数据的数据

1 个答案: