问题描述
我有下表和一些数据:
表格:
create table tbl_jsontest
(
id int,jdata json
);
记录:
insert into tbl_jsontest values(1,'{"Id":1,"Name":"Jack"}');
insert into tbl_jsontest values(1,'[{"Id":2,"Name":"Mak"},{"Name":"Aez","Address":"ZX"}]');
insert into tbl_jsontest values(1,'[{"Id":5,"Name":"Lee"}]');
查询:
SELECT json_data.key AS key1,json_data.value AS value1
FROM tbl_jsontest,json_each_text(tbl_jsontest.jdata) AS json_data;
出现错误:
错误:无法将数组解构为对象
解决方法
json_each_text 函数接受一个 json 对象作为输入,并且不适用于数组。
文档https://www.postgresql.org/docs/current/functions-json.html
json_each_text ( json ) → setof record ( key text,value text )
将顶级 JSON 对象扩展为一组键/值对。返回的值将是文本类型。
可以先用json_array_elements
展开数组,然后展开对象
你也应该将 jdata 重新格式化为相同的格式
记录:
insert into tbl_jsontest values(1,'[{"Id":1,"Name":"Jack"}]');
insert into tbl_jsontest values(1,'[{"Id":2,"Name":"Mak"},{"Name":"Aez","Address":"ZX"}]');
insert into tbl_jsontest values(1,'[{"Id":5,"Name":"Lee"}]');
查询:
select t.id,key,value
from (SELECT id,json_array_elements(tbl_jsontest.jdata) d
FROM tbl_jsontest) t,json_each_text(t.d);
结果:
+--+-------+-----+
|id|key |value|
+--+-------+-----+
|1 |Id |2 |
|1 |Name |Mak |
|1 |Name |Aez |
|1 |Address|ZX |
|1 |Id |5 |
|1 |Name |Lee |
|1 |Id |1 |
|1 |Name |Jack |
+--+-------+-----+