Sql 如何优化将表与其自身连接起来的红移查询？

假设我有一个事务表

CREATE TABLE IF NOT EXISTS txn_raw (
transaction_id VARCHAR(60),
sport_label VARCHAR(300),
family_label VARCHAR(150),
item_label VARCHAR(150)
)
DISTKEY (the_transaction_id)
SORTKEY (the_transaction_id, sport_label, family_label, item_label)
;
COMMIT;

我想优化以下查询，以便计算项目之间的相关性

SELECT 
a.sport_label as sport_label_a, 
a.family_label as family_label_a, 
a.dsm_label as dsm_label_a, 
b.sport_label as sport_label_b, 
b.family_label as family_label_b, 
b.dsm_label as dsm_label_b, 
count(distinct a.the_transaction_id) as txn_ab
FROM txn_raw a
JOIN txn_raw b 
on a.the_transaction_id=b.the_transaction_id
and a.sport_label != b.sport_label
and a.family_label != b.family_label
and a.item_label != b.item_label
group by 1,2,3,4,5,6

我正在考虑在将txn_raw与自身连接后创建一个临时表来存储数据。 然后查询临时表并按分组

---

有没有更好的方法来优化这种查询？

我建议在加入之前提取不同的值，而不是之后：

WITH r as (
      SELECT DISTINCT the_transaction_id, sport_label, family_label, item_label
      FROM txn_raw
     )
SELECT a.sport_label as sport_label_a, 
       a.family_label as family_label_a, 
       a.dsm_label as dsm_label_a, 
       b.sport_label as sport_label_b, 
       b.family_label as family_label_b, 
       b.dsm_label as dsm_label_b, 
       COUNT(*) as txn_ab
FROM r a JOIN 
     r b 
     ON a.the_transaction_id = b.the_transaction_id AND
        a.sport_label <> b.sport_label AND
        a.family_label <> b.family_label AND
        a.item_label <> b.item_label
GROUP BY 1,2,3,4,5,6;

---

那就是。任何一列都不同，但不是所有列。

您似乎已经有一个涵盖所有4列的索引。是吗？请提供示例数据和所需结果。您应该查看并提供查询的解释计划和实际执行时间。因为你问了一个优化问题，我想查询时间太长了。第一个问题是为什么。知道了这一点，接下来该怎么办了。谢谢！我可以知道为什么最好先做区分的原因吗？@LouisLaw。防止行的增加，这只会降低后续处理的速度。

FROM r a JOIN 
     r b 
     ON a.the_transaction_id = b.the_transaction_id AND
        NOT (a.sport_label = b.sport_label AND
             a.family_label = b.family_label AND
             a.item_label = b.item_label
            )