postgresql – Postgres查询结果到json对象

发布时间：2020-12-13 15:59:17 所属栏目：百科来源：网络整理

导读：我的查询如下 SELECT w.payload,Count('payload') OVER () AS ROWCOUNTFROM wholesale_confirmation.wholesale_order_confirmation wWHERE w.delivery_date = COALESCE(NULL,w.delivery_date) AND w.ship_to_location_id = COALESCE(NULL,w.ship_to_location

我的查询如下

SELECT w.payload,Count('payload') OVER () AS ROWCOUNT
FROM wholesale_confirmation.wholesale_order_confirmation w
WHERE w.delivery_date = COALESCE(NULL,w.delivery_date)
  AND w.ship_to_location_id = COALESCE(NULL,w.ship_to_location_id)
  AND w.order_raised_date = COALESCE(NULL,w.order_raised_date)
  AND w.ship_from_location_id = COALESCE(NULL,w.ship_from_location_id)
LIMIT 10
OFFSET 0;

这给我的结果是这样的：

Result

我想要{“payload：”[payload1,payload2,payload3],“rowcount”：n}.

Postgres版本10.3,有效载荷数据类型是jsonb

解决方法

COALESCE(NULL,w.delivery_date)归结为w.delivery_date.

因此WHERE w.delivery_date = COALESCE(NULL,w.delivery_date)归结为WHERE w.delivery_date IS NOT NULL.

Count(‘payload’)OVER()AS ROWCOUNT只是一种嘈杂的方式,表示count(*)OVER()AS rowcount并返回结果的总行数.

您当前的查询,简化：

SELECT payload,count(*) OVER () AS rowcount
FROM   wholesale_confirmation.wholesale_order_confirmation
WHERE  delivery_date          IS NOT NULL
AND    ship_to_location_id    IS NOT NULL
AND    order_raised_date      IS NOT NULL
AND    ship_from_location_id  IS NOT NULL
LIMIT  10;

要获取更新后的问题中的JSON对象,包含一个JSON对象数组和总行数：

SELECT json_build_object('payload',jsonb_agg(payload),'rowcount',min(rowcount))
FROM  (
   SELECT payload,count(*) OVER () AS rowcount
   FROM   wholesale_confirmation.wholesale_order_confirmation
   WHERE  delivery_date          IS NOT NULL
   AND    ship_to_location_id    IS NOT NULL
   AND    order_raised_date      IS NOT NULL
   AND    ship_from_location_id  IS NOT NULL
   LIMIT  10
   ) sub;

> Best way to get result count before LIMIT was applied

如果要处理许多行,LIMIT / OFFSET的性能会降低.考虑更复杂的分页技术：

> Optimize query with OFFSET on large table

（编辑：李大同）

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