Postgres中的GROUP BY-JSON数据类型不相等吗？

Question

我在匹配表中有以下数据：

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]}

我想按名称在表中选择每个最后一个不同的团队。即我想要一个查询，将返回：

6;{"Name":"TeamA","Players":[{"Name":"CCC"},{"Name":"BBB"}
6;{"Name":"TeamB","Players":[{"Name":"AAA"},{"Name":"DDD"}

因此，上次出现该团队的每个团队都显示在表格中。
我一直在使用以下内容：

WITH t AS (SELECT id, json_array_elements(match->'Teams') AS team FROM matches)
SELECT MAX(id) AS max_id, team FROM t GROUP BY team->'Name';

但这返回：

ERROR: could not identify an equality operator for type json
SQL state: 42883
Character: 1680

我知道Postgres没有JSON的相等性。我只需要团队名称（字符串）相等即可，无需比较该团队的球员。

任何人都可以建议其他方法吗？
以供参考：

SELECT id, json_array_elements(match->'Teams') AS team FROM matches

返回：

5;"{"Name":"TeamA","Players":[{"Name":"AAA"},{"Name":"BBB"}]}"
5;"{"Name":"TeamB","Players":[{"Name":"CCC"},{"Name":"DDD"}]}"
6;"{"Name":"TeamA","Players":[{"Name":"CCC"},{"Name":"BBB"}]}"
6;"{"Name":"TeamB","Players":[{"Name":"AAA"},{"Name":"DDD"}]}"

编辑：我投与到text并遵循此问题，我DISTINCTON代替GROUP BY。这是我的完整查询：

WITH t AS (SELECT id, json_array_elements(match->'Teams') AS team
           FROM matches ORDER BY id DESC)
SELECT DISTINCT ON (team->>'Name') id, team FROM t;

返回上面我想要的。有谁有更好的解决方案？

Answer 1

通过联接可以更短，更快，更优雅LATERAL：

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;  -- to get the "last"

JSON和平等

jsonPostgres中没有数据类型的相等运算符，但是jsonb（Postgres 9.4+）有一个运算符