Question

我想使用MySQL创建以下两个查询的INTERSECTion：

1) SELECT atn_nid, atn_select_flag, atn_image_name
FROM city, attraction WHERE cty_nid = atn_cty_nid AND cty_nid = 5;

2) SELECT atn_nid, s2a_image_select_flag, atn_image_name 
FROM segment, seg2atn, attraction WHERE seg_nid = s2a_seg_nid AND
s2a_atn_nid = atn_nid and seg_nid = 68 AND
s2a_image_select_flag = true;

注意：查询1中的atn_select_flag和s2a_image_select_flag都是布尔值

由于MYSQL由于某种原因不支持INTERSECT，我对用于实现此目的的语法感到茫然。任何帮助将不胜感激。

Answer 1

如果我正确地假设：

名为atn_...，cty_...，seg_...和s2a_...的字段属于attraction，city，segment，以及分别为seg2atn。
名为..._nid的字段是主键。
atn_cty_nid，s2a_seg_nid等是外键。

然后您的第一个查询等同于：

SELECT atn_nid, atn_select_flag, atn_image_name
  FROM attraction
 WHERE aty_cty_nid = 5
;

并且您的第二个查询等同于：

SELECT atn_nid, TRUE, atn_image_name
  FROM attraction
 WHERE atn_id IN
        ( SELECT s2a_atn_nid
            FROM seg2atn
           WHERE s2a_seg_nid = 68
             AND s2a_image_select_flag = TRUE
        )
;

所以他们的交集就是这样：

SELECT atn_nid, TRUE AS atn_select_flag, atn_image_name
  FROM attraction
 WHERE atn_cty_nid = 5
   AND atn_nid IN
        ( SELECT s2a_atn_nid
            FROM seg2atn
           WHERE s2a_seg_nid = 68
             AND s2a_image_select_flag = TRUE
        )
;

和（编辑添加）他们的联盟就是这样：

SELECT atn_nid, atn_select_flag, atn_image_name
  FROM attraction
 WHERE aty_cty_nid = 5
UNION
SELECT atn_nid, TRUE, atn_image_name
  FROM attraction
 WHERE atn_id IN
        ( SELECT s2a_atn_nid
            FROM seg2atn
           WHERE s2a_seg_nid = 68
             AND s2a_image_select_flag = TRUE
        )
;

使用可比较列的MySQL中的INTERSECT

1 个答案: