sql - 在多个查询上使用 "with"语句？

Question

我正在尝试从我的表中删除重复的行，例如，如果我的客户表包含以下内容:

first_name    last_name    email 
fred          wilford      wilford@xchange.co.uk
fred          wilford      wilford@xchange.co.uk
Damian        Jones        jones@xchange.co.uk

理想的结果应该是这样的:

first_name    last_name    email 
fred          wilford      wilford@xchange.co.uk
Damian        Jones        jones@xchange.co.uk

在删除主表中的重复行之前，对于创建的包含重复行的中间表来说，这应该是相当简单的，最后将中间表中的所有行插入回主表。但是我更愿意删除中间表并只使用类似 with 语句的东西。 考虑以下示例:

with dups as 
(
    select name,last_name,email from customer group by 1,2,3 having  
    count(*) > 1 
)
delete from customer
using
(
    select name,last_name,email from customer group by 1,2,3 having     
    count(*) > 1 
)b
where b.name = customer.name;
insert into customer
(
    select name,last_name,email from dups
)

问题是最后的插入语句失败了，因为“dups”没有被识别。有没有办法来解决这个问题？提前致谢

Answer 1

您可以 chain the CTE如果你想:

WITH dups AS
(
    select name,last_name,email from customer group by 1,2,3 having  
    count(*) > 1 
),
del AS(
    DELETE FROM customer USING dups WHERE dups.name = customer.name RETURNING dups.*
),
ins AS(
    INSERT INTO customer(name,last_name,email) SELECT name,last_name,email FROM del RETURNING del.*
)
SELECT * FROM ins;