大表的SQL查詢

Question

需要幫助在SQL數據庫中查找相似的值。 表結構如下：

    id         |        item_id_nm |      height |    width |     length |     weight
    ----------------------------------------------------------------------------------
    1          |       00000000001 |      1.0    |     1.0  |        1.0 |         1.0
    2          |       00000000001 |      1.1    |     1.0  |        0.9 |         1.1
    3          |       00000000001 |      2.0    |     1.0  |        1.0 |         1.0
    4          |       00000000002 |      1.0    |     1.0  |        1.0 |         1.0
    5          |       00000000002 |      1.0    |     1.1  |        1.1 |         1.0
    6          |       00000000002 |      1.0    |     1.0  |        1.0 |         2.0

id顯然不能重復，item_id_nm可以重復（實際上可以多次發生，也就是> 2）。

您將如何形成SQL以查找重復的item_id_nm，但僅當高度或寬度，長度或重量的值相差> 30％時才查找。

我知道它需要遍歷表，但是我該如何進行檢查。 謝謝您的幫助。

編輯：包含％30差異的示例。 id = 3，其高度與id的1和2的1.0（或1.1）相差200％。因此，抱歉，不清楚，但是對於高度，寬度，長度或重量的每個值，可能會有30％的差異。如果其中一個有30％的差異，則將其視為另一個的重復。

Answer 1

這應該使您的行與平均值相差30％或更多：

SELECT t1.*
FROM tbl t1
INNER JOIN (
    SELECT
         item_id_nm,
        AVG(width) awidth, AVG(height) aheight, 
        AVG(length) alength, AVG(weight) aweight
    FROM tbl
    GROUP BY item_id_nm ) t2
USING (item_id_nm)
WHERE 
    width > awidth * 1.3 OR width < awidth * 0.7
    OR height > aheight * 1.3 OR height < aheight * 0.7
    OR length > alength * 1.3 OR length < alength * 0.7
    OR weight > aweight * 1.3 OR weight < aweight * 0.7

這應該給您幾行相差30％的行：

SELECT t1.*,t2.*
FROM tbl t1
INNER JOIN tbl t2
USING (item_id_nm)
WHERE 
     (t1.width > t2.with * 1.3 OR t1.width < t2.width * 0.7)
    OR (t1.height > t2.height * 1.3 OR t1.height < t2.height * 0.7)
    OR (t1.length > t2.length * 1.3 OR t1.length < t2.length * 0.7)
    OR (t1.weight > t2.weight * 1.3 OR t1.weight < t2.weight * 0.7)

Answer 2

我認為您可以使用以下方式：

SELECT item_id_nm
FROM yourtable
GROUP BY item_id_nm
HAVING
  MIN(height)*1.3 < MAX(height) OR
  MIN(width)*1.3 < MAX(width) OR
  MIN(length)*1.3 < MAX(length) OR
  MIN(weight)*1.3 < MAX(weight)

Answer 3

SELECT
    *
FROM
    TableName
WHERE
   (height > 1.3 * width OR height < 0.7 width) OR
   (length > 1.3 * width OR length < 0.7 width)
GROUP BY
    item_id_nm
HAVING
    COUNT(item_id_nm) > 1

Answer 4

我會用：

SELECT s1.id AS id1, s2.id AS id2
, s1.height AS h1, s2.height as h2
, s1.width as width1, s2.width as width2
, s1.length as l1, s2.length as l2
, s1.weight as weight1, s2.weight as weight2
FROM stack s1
INNER JOIN stack s2
ON s1.item_id_nm = s2.item_id_nm
WHERE s1.id != s2.id
AND s1.id < s2.id
AND (abs(100-((s2.height*100)/s1.height)) > 30
OR abs(100-((s2.width*100)/s1.width)) > 30
OR abs(100-((s2.length*100)/s1.length)) > 30
OR abs(100-((s2.weight*100)/s1.weight)) > 30)

使用PostgreSQL（ http://sqlfiddle.com/#!12/e5f25/15 ）。 此代碼不返回重復的行。