在 string_agg 函数中使用 if 语句 - postgreSQL

Question

查询如下

WITH notes AS (
    SELECT 891090 Order_ID, False customer_billing,  false commander, true agent 
    UNION ALL
    SELECT 891091, false, true, true 
    UNION ALL
    SELECT 891091, true, false, false)

SELECT
  n.order_id,
  string_Agg(distinct CASE
    WHEN n.customer_billing = TRUE THEN 'AR (Customer Billing)'
    WHEN n.commander = TRUE THEN 'AP (Commander)'
    WHEN n.agent = TRUE THEN 'AP (Agent)'
    ELSE NULL
  END,', ') AS finance
FROM notes n
WHERE
 n.order_id = 891091 AND (n.customer_billing = TRUE or n.commander = TRUE or n.agent = TRUE)
 GROUP BY ORDER_ID

如您所见，有两条记录 order_id 为 891091.

第一个 891091 条记录 commander 和 agent 设置为真
第二个 891091 记录已 customer_billing 设置为 true

由于使用了switch case，所以只考虑第一个真值和returnscommander，不考虑agent.

所以输出变成

order_id    finance
891091  AP (Commander), AR (Customer Billing)

dbfiddle.uk Example

我需要考虑记录中的所有真实值，以便输出变为

order_id    finance
    891091  AP (Commander), AP (Agent), AR (Customer Billing)

我最初的想法是使用 if 语句而不是 case 语句可以解决这个问题。我不确定如何在 string_agg 函数

中执行此操作

如何实现？

编辑 1：

下面指定的答案几乎可以正常工作。但问题是逗号分隔值不是 distinct

这是更新后的 fiddle https://dbfiddle.uk/?rdbms=postgres_14&fiddle=9647d92870e3944516172eda83a8ac6e

Answer 1

你可以考虑把你的case拆分成单独的，用数组来收集。然后可以用array_to_string格式化：

WITH notes AS (
  SELECT 891090 Order_ID, False customer_billing,  false commander, true agent UNION ALL
  SELECT 891091, false, true, true UNION ALL
  SELECT 891091, true, true, false),
tmp as (
SELECT
  n.order_id id,
      array_agg(
        ARRAY[
          CASE WHEN n.customer_billing = TRUE THEN 'AR (Customer Billing)' END,
          CASE WHEN n.commander = TRUE THEN 'AP (Commander)' END,
          CASE WHEN n.agent = TRUE THEN 'AP (Agent)' END
        ]) AS finance_array
FROM notes n
WHERE
 n.order_id = 891091 AND (n.customer_billing = TRUE or n.commander = TRUE or n.agent = TRUE)
 GROUP BY ORDER_ID )
 select id, array_to_string(array(select distinct e from unnest(finance_array) as a(e)), ', ')
 from tmp;

这里是db_fiddle.

在 string_agg 函数中使用 if 语句 - postgreSQL

Using if statement in string_agg function - postreSQL

sql

postgresql

aggregate-functions