Question

我有类似的查询，我需要查找特定客户在一个时间范围内的交易数量：

select customer_id, count(transactions)
from transactions
where customer_id = 'FKJ90838485'
and purchase_date between '01-JAN-13' and '31-AUG-13'
group by customer_id

表事务未在customer_id上编制索引，而是另一个名为transaction_id的字段。 Customer_ID是字符类型，而transaction_id是数字。

'accounting_month'字段也被编入索引..此字段仅存储交易发生的月份...即，purchase_date = '03 -MAR-13'将具有accounting_month = '01 -MAR-13'

交易表在'01 -JAN-13'和'31 -AUG-13'的时间范围内有大约2000万条记录

当我运行上述查询时，它需要超过40分钟才能回来，有任何想法或提示吗？

Answer 1

正如其他人已经评论过的那样，最好是添加一个覆盖查询的索引，所以：

请与数据库管理员联系并请求他们在(customer_id, purchase_date)上添加索引，因为查询正在执行表扫描。

图片的标题说明：

使用日期而不是字符串文字（您可能已经知道并且已经这样做了，这里仍然为未来的读者注意）

您不必将customer_id放在SELECT列表中，如果从那里删除它，也可以从GROUP BY删除它，以便查询变为：

select count(*) as number_of_transactions
from transactions
where customer_id = 'FKJ90838485'
  and purchase_date between DATE '2013-01-01' and DATE '2013-08-31' ;

如果您在WHERE上没有customer_id条件，则可以在GROUP BY和SELECT列表中创建select customer_id, count(*) as number_of_transactions from transactions where purchase_date between DATE '2013-01-01' and DATE '2013-08-31' group by customer_id ;条件将计算每个客户的交易数量。以上建议的指数也有助于此：
```
{{1}}
```

Answer 2

这只是我想到的一个想法。它可能会起作用，尝试运行它，看看它是否比你现有的有所改进。

我正在尽可能地使用你所说的transaction_id索引。

WITH min_transaction (tran_id)
AS (
   SELECT MIN(transaction_ID)
   FROM TRANSACTIONS
   WHERE
      CUSTOMER_ID = 'FKJ90838485'
      AND purchase_date >= '01-JAN-13'
   ), max_transaction (tran_id)
AS (
   SELECT MAX(transaction_ID)
   FROM TRANSACTIONS
   WHERE 
      CUSTOMER_ID = 'FKJ90838485'
      AND purchase_date <= '31-AUG-13'
   )
SELECT customer_id, count(transaction_id)
FROM transactions
WHERE
   transaction_id BETWEEN min_transaction.tran_id AND max_transaction.tran_id
GROUP BY customer_ID

Answer 3

这可能会更快，因为它会查看范围的transaction_id而不是purchase_date。我还考虑到accounting_month被编入索引：

select customer_id, count(*)
from transactions
where customer_id = 'FKJ90838485'
and transaction_id between (select min(transaction_id)
                            from transactions
                           where accounting_month = '01-JAN-13' 
                           )  and
                           (select max(transaction_id)
                            from transactions
                           where accounting_month = '01-AUG-13' 
                           ) 
group by customer_id

也许你也可以尝试：

select customer_id, count(*)
from transactions
where customer_id = 'FKJ90838485'
and accounting_month between '01-JAN-13' and '01-AUG-13'
group by customer_id

使用非索引列的SQL计数查询

3 个答案: