关注this post ,我有一个返回下表的 SQL 查询:
team (json)
"{"Name":"TeamA","Players":[{"Name":"CCC"},{"Name":"BBB"}]}"
"{"Name":"TeamB","Players":[{"Name":"AAA"},{"Name":"DDD"}]}"
我需要将其聚合为 JSON 以在我的应用程序中使用。我正在使用以下内容:
SELECT json_agg(u) FROM (SELECT DISTINCT ON (t.team->>'Name') t.team
FROM matches m, json_array_elements(m.match->'Teams') t(team)
ORDER BY t.team->>'Name', m.id DESC) AS u
返回结果:
"[{"team":{"Name":"TeamA","Players":[{"Name":"CCC"},{"Name":"BBB"}]}},
{"team":{"Name":"TeamB","Players":[{"Name":"AAA"},{"Name":"DDD"}]}}]"
看来它在每个对象之前放置了一个“团队”标签。这在我的 C# 应用程序中无法正确序列化。看完this question我相信这可能不是正确的 JSON。这是正确的吗?
我想以以下形式获取它:
"[{"Name":"TeamA","Players":[{"Name":"CCC"},{"Name":"BBB"}]},
{"Name":"TeamB","Players":[{"Name":"AAA"},{"Name":"DDD"}]}]"
我相信这是正确的 JSON,它将在我的应用程序中正确解析。
我在 C# 中使用的类如下:
//[JsonObject(Title="team")] I tried adding this too
public class Team
{
public string Name { get; set; }
public List<Player> Players { get; set; }
}
这是正确的 JSON,我需要修复我的 C# 类吗?或者它是否不正确,如何从 json_agg 输出中删除列标题?
更新:
这是我的表结构:
CREATE TABLE matches
(
id serial NOT NULL,
match json,
CONSTRAINT matches_pkey PRIMARY KEY (id)
)
示例数据:
5;{"Id":1,"Teams":[{"Name":"TeamA","Players":[{"Name":"AAA"},{"Name":"BBB"}]},{"Name":"TeamB","Players":[{"Name":"CCC"},{"Name":"DDD"}]}],"TeamRank":[1,2]}
6;{"Id":2,"Teams":[{"Name":"TeamA","Players":[{"Name":"CCC"},{"Name":"BBB"}]},{"Name":"TeamB","Players":[{"Name":"AAA"},{"Name":"DDD"}]}],"TeamRank":[1,2]}
请参阅this question了解更多。
最佳答案
从某种意义上说,它是正确的 JSON,它是有效的,但它显然不是您想要的。所以答案取决于“正确”的定义。我们将假设您想要的是“正确的”。
您要求它聚合 u
,这是一个包含 team
列的结果集。这意味着它必须将此信息添加到结果中。您应该只要求聚合 u.team
,这是您想要的字段。然后你就会得到你想要的结果。
WITH matches as
(
select 5 as id, '{"Id":1,"Teams":[{"Name":"TeamA","Players":[{"Name":"AAA"},{"Name":"BBB"}]},{"Name":"TeamB","Players":[{"Name":"CCC"},{"Name":"DDD"}]}],"TeamRank":[1,2]}'::json as match
union all
select 6 as id, '{"Id":2,"Teams":[{"Name":"TeamA","Players":[{"Name":"CCC"},{"Name":"BBB"}]},{"Name":"TeamB","Players":[{"Name":"AAA"},{"Name":"DDD"}]}],"TeamRank":[1,2]}' as match
)
SELECT json_agg(u.team) FROM (
SELECT DISTINCT ON (t.team->>'Name') t.team
FROM matches m, json_array_elements(m.match->'Teams') t(team)
ORDER BY t.team->>'Name', m.id DESC) AS u;
结果:
[{"Name":"TeamA","Players":[{"Name":"CCC"},{"Name":"BBB"}]},
{"Name":"TeamB","Players":[{"Name":"AAA"},{"Name":"DDD"}]}]
关于c# - Postgres json_agg 包含列标题 - JSON 不正确?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/30521196/