将 CTE 查询转换为普通查询

Question

我想将我的@PostgreSQL、CTE 查询转换为普通查询，因为 cte 函数主要用于数据仓库 SQL，对于 Postgres 生产 DBS 效率不高。因此，需要帮助将此 CTE 查询转换为普通查询

WITH
cohort AS (
    SELECT
        *
    FROM (
        select 
        activity_id,
        ts,
        customer,
        activity,
        case 
        when activity = 'completed_order' and lag(activity) over (partition by customer order by ts) != 'email' 
        then null
        when activity = 'email' and lag(activity) over (partition by customer order by ts) !='email' 
        then 1
        else 0
    end as cndn
        
        from activity_stream where customer in (select customer from activity_stream where activity='email') 
        order by ts
) AS s 

)
(
    select 
        *               
      from cohort as s
where cndn = 1 OR cndn is null order by ts)

Answer 1

您可以将 CTE 内联到您的外部查询中：

select *               
from
(
    select activity_id, ts, customer, activity,
           case when activity = 'completed_order' and lag(activity) over (partition by customer order by ts) != 'email' 
                then null
                when activity = 'email' and lag(activity) over (partition by customer order by ts) !='email' 
                then 1
                else 0
           end as cndn
    from activity_stream
    where customer in (select customer from activity_stream where activity = 'email') 
) as s
where cndn = 1 OR cndn is null
order by ts;

请注意，您在 CTE 中有一个不必要的子查询，它执行的 ORDER BY 无论如何都不会“坚持”。但除此之外，您可能希望保持当前代码不变。

将 CTE 查询转换为普通查询

Convert CTE Query into normal Query

sql

postgresql

common-table-expression