从SQL表中选择行，从另一个表中选择5行

Question

我有三个这样的SQL Server表

我需要categories from LS_categoires where nodeid = 183选择categories from LS_categoires where nodeid = 183并select only 5 files from LS_files与每个类别相关的select only 5 files from LS_files中select only 5 files from LS_files

如果我有两个与node 183有关的类别，结果应该是10 rows吗？

Answer 1

尝试这个：

  SELECT
  *  
FROM LS_Categories c 
INNER JOIN
( 
   SELECT 
     *, ROW_NUMBER() OVER(PARTITION BY catid
                          ORDER BY item_id ASC) rownum
   FROM LS_ItemTypes
) l  ON c.catid = l.catid
    AND l.rownum <= 5
INNER JOIN LS_Files f ON l.item_id = f.id
where c.nodeid = 183;

这将为每个类别选择第一个文件。