我正在尝试将多行分组在一起以形成一个新表。我这样做是为了找到每个客户的每种发票交付方式的数量。
我已经尝试过此代码
CREATE TABLE new_table AS
SELECT customer_id,
(COUNT(invoice_send_method WHERE invoice_send_method='Fax' GRPUP BY(purchase_date || '_' || item_id))),
(COUNT(invoice_send_method WHERE invoice_send_method='Mail' GRPUP BY(purchase_date || '_' || item_id))),
(COUNT(invoice_send_method WHERE invoice_send_method='Email' GRPUP BY(purchase_date || '_' || item_id)))
FROM my_table;
但是它会在invoice_send_method的第一个实例之后(在WHERE之前)返回语法错误。
为了算作发票发送方式的一个实例,我创建了一个规则,该规则必须是purchase_date和item_id的唯一组合。
有更好的方法吗?似乎我无法在COUNT中引入WHERE或GROUP BY语句,但是在仍然检查所有发票传送方式的同时,我不知道该怎么办。
我正在使用MySQL Workbench。
答案 0 :(得分:0)
您可以尝试使用ORDER BY代替GROUP BY:
CREATE TABLE new_table AS
SELECT customer_id, purchase_date, item_id,
COUNT(invoice_send_method WHERE invoice_send_method='Fax') as count_fax,
COUNT(invoice_send_method WHERE invoice_send_method='Mail') as count_mail,
COUNT(invoice_send_method WHERE invoice_send_method='Email') as count_email,
FROM my_table
ORDER BY purchase_date, item_id;
如果您不想看到它们,可以从SELECT中删除purchase_date和item_id,这样更容易测试。
答案 1 :(得分:0)
您的查询在语法上是错误的。
使用这个:
CREATE TABLE new_table AS
SELECT
t.customer_id,
SUM(t.invoice_send_method = 'Fax') fax_count,
SUM(t.invoice_send_method = 'Mail') mail_count,
SUM(t.invoice_send_method = 'Email') email_count
FROM (SELECT DISTINCT * FROM my_table) AS t
GROUP BY t.customer_id;
请参见demo。
结果:
| customer_id | fax_count | email_count | mail_count |
| ----------- | --------- | ----------- | ---------- |
| 10863865 | 0 | 1 | 0 |
| 12010467 | 1 | 0 | 0 |
| 2771929 | 0 | 0 | 3 |
| 5317588 | 0 | 0 | 1 |
| 7484618 | 0 | 3 | 0 |
| 7924567 | 1 | 0 | 0 |
| 9320463 | 1 | 0 | 0 |