按字符长度选择

Question

我必须选择points>0但包含在points=0的短语中的最长短语，如果查看演示，则输出中的行将是数字3和6：

http://sqlfiddle.com/#!18/e954f/1/0

提前谢谢了。

Answer 1

您可以使用内部联接将短语与LIKE进行比较，以仅获取包含在另一个短语中的短语。 在WHERE子句中过滤点。 然后从连接的实例中获取由短语划分的rank() ，并按长度递减的顺序排序。 在外部SELECT仅获得等级为1的那些。

SELECT x.id,
       x.phrase,
       x.points
       FROM (SELECT w1.id,
                    w1.phrase,
                    w1.points,
                    rank() OVER (PARTITION BY w2.phrase
                                 ORDER BY len(w1.phrase) DESC) r
                    FROM words w1
                         INNER JOIN words w2
                                    ON w2.phrase LIKE concat(w1.phrase, '%')
                    WHERE w2.points = 0
                          AND w1.points > 0) x
       WHERE x.r = 1;

SQL小提琴

---

编辑：

包括其他短语：

SELECT x.id,
       x.phrase,
       x.other_phrase,
       x.points
       FROM (SELECT w1.id,
                    w1.phrase,
                    w2.phrase other_phrase,
                    w1.points,
                    rank() OVER (PARTITION BY w2.phrase
                                 ORDER BY len(w1.phrase) DESC) r
                    FROM words w1
                         INNER JOIN words w2
                                    ON w2.phrase LIKE concat(w1.phrase, '%')
                    WHERE w2.points = 0
                          AND w1.points > 0) x
       WHERE x.r = 1;

Answer 2

您可以使用CTE查找所有带有正点的短语，这些短语是具有0点的短语的子字符串。 然后，您可以找到与每个0点短语相关联的子字符串的最大长度，并将其JOIN回CTE以获取与该条件匹配的短语：

WITH cte AS (
SELECT w1.*, w2.id AS w2_id
FROM words w1
JOIN (SELECT * 
      FROM words
      WHERE points = 0) w2 ON w1.phrase = LEFT(w2.phrase, LEN(w1.phrase))
WHERE w1.points > 0
)
SELECT cte.id, cte.phrase, points
FROM cte
JOIN (SELECT w2_id, MAX(LEN(phrase)) AS max_len
      FROM cte
      GROUP BY w2_id) cte_max ON cte_max.w2_id = cte.w2_id AND cte_max.max_len = LEN(cte.phrase)

输出：

id  phrase              points
3   tool box online     1
6   stone road          1

更新了SQLFiddle

Answer 3

您将从短语的最大长度到最小长度，其中points>0

SELECT *, LEN(phrase) AS Lenght FROM words where points>0 ORDER BY LEN(phrase) DESC

如果你想要最长的短语

 SELECT TOP 1 *, LEN(phrase) AS Lenght FROM words where points>0 ORDER BY LEN(phrase) DESC