如何將此嵌套集SQL查詢轉換爲LINQ查詢？

Question

查詢Nested Set Model table，這裏是SQL ...這怎麼寫在LINQ中？

SELECT parent.name 
FROM nested_category AS node, nested_category AS parent 
WHERE node.lft BETWEEN parent.lft AND parent.rgt 
AND node.name = 'FLASH' 
ORDER BY parent.lft; 

特別是，FROM部分...從來沒有嘗試過像LINQ那樣的事情。

Answer 1

也許是這樣的：

var query = from node in nested_category 
      from parentNode in nested_category 
      where node.lft >= parentNode.lft && node.rgt <= parentNode.rgt 
       && node.name == "FLASH" 
      orderby parent.left 
      select parent.name; 

Answer 2

如果你做左外連接類似的（即不使用爲和DefaultIfEmpty（）），那麼頂級父節點將不會被輸出（因爲它的父母是NULL）

我的SQL版本去：

SELECT 
    B.ELEMENT_CODE ParentElement, 
    A.ELEMENT_CODE ChildElement 
FROM NESTED_SET_STRUCTURE AS A 
LEFT OUTER JOIN NESTED_SET_STRUCTURE AS B 
    ON B.PROCEDURE = 'TEST1' AND B.FROM_LEFT = (SELECT MAX(C.FROM_LEFT) 
      FROM NESTED_SET_STRUCTURE AS C 
      WHERE C.PROCEDURE = 'TEST1' AND A.FROM_LEFT > C.FROM_LEFT 
       AND A.FROM_LEFT < C.TO_RIGHT) 
WHERE 
    A.PROCEDURE = 'TEST1'; 

翻譯爲：

var nestedSets1 = 
    from a in NESTED_SET_STRUCTUREs 
    join b in NESTED_SET_STRUCTUREs on 
    new { a.PROCEDURE, FROM_LEFT = ((from c in NESTED_SET_STRUCTUREs 
     where c.PROCEDURE.Equals("TEST1") 
     && a.FROM_LEFT > c.FROM_LEFT 
     && a.FROM_LEFT < c.TO_RIGHT 
     select (c.FROM_LEFT)).Max()) } equals 
    new { b.PROCEDURE, b.FROM_LEFT } into bo 
    from bb in bo.DefaultIfEmpty() 
    where 
     a.PROCEDURE.Equals("TEST1") 
    orderby a.FROM_LEFT 
    select new { 
     ParentElement = bb.ELEMENT_CODE, 
     ChildElement = a.ELEMENT_CODE 
    }; 

希望幫助，保羅。