使用postgresql 9.3我可以选择JSON数据类型的特定字段,但如何使用UPDATE修改它们?我在postgresql文档或网上任何地方都找不到这样的例子。我尝试了一些显而易见的方法:

postgres=# create table test (data json);
CREATE TABLE
postgres=# insert into test (data) values ('{"a":1,"b":2}');
INSERT 0 1
postgres=# select data->'a' from test where data->>'b' = '2';
 ?column?
----------
 1
(1 row)
postgres=# update test set data->'a' = to_json(5) where data->>'b' = '2';
ERROR:  syntax error at or near "->"
LINE 1: update test set data->'a' = to_json(5) where data->>'b' = '2...

当前回答

如果你想在你的JSON更新命令中使用其他列的值,你可以使用字符串连接:

UPDATE table
SET column1 = column1::jsonb - 'key' || ('{"key": ' || column2::text ||  '}')::jsonb
where ...;

其他回答

遗憾的是,我没有在文档中找到任何东西,但您可以使用一些变通方法,例如您可以编写一些扩展函数。

例如,在Python中:

CREATE or REPLACE FUNCTION json_update(data json, key text, value json)
returns json
as $$
from json import loads, dumps
if key is None: return data
js = loads(data)
js[key] = value
return dumps(js)
$$ language plpython3u

然后

update test set data=json_update(data, 'a', to_json(5)) where data->>'b' = '2';

你可以尝试更新如下:

格式:UPDATE table_name SET column_name = column_name::jsonb || '{"key":new_value}' WHERE column_name条件;

举个例子:

UPDATE test SET data = data::jsonb || '{"a":new_value}' WHERE data->>'b' = '2';

即使下面的函数不能满足这个请求(函数json_object_agg在PostgreSQL 9.3中不可用),下面的函数对于任何为PostgreSQL 9.4寻找||运算符的人来说都是有用的,因为在即将到来的PostgreSQL 9.5中实现了:

CREATE OR REPLACE FUNCTION jsonb_merge(left JSONB, right JSONB)
RETURNS JSONB
AS $$
SELECT
  CASE WHEN jsonb_typeof($1) = 'object' AND jsonb_typeof($2) = 'object' THEN
       (SELECT json_object_agg(COALESCE(o.key, n.key), CASE WHEN n.key IS NOT NULL THEN n.value ELSE o.value END)::jsonb
        FROM jsonb_each($1) o
        FULL JOIN jsonb_each($2) n ON (n.key = o.key))
   ELSE 
     (CASE WHEN jsonb_typeof($1) = 'array' THEN LEFT($1::text, -1) ELSE '['||$1::text END ||', '||
      CASE WHEN jsonb_typeof($2) = 'array' THEN RIGHT($2::text, -1) ELSE $2::text||']' END)::jsonb
   END     
$$ LANGUAGE sql IMMUTABLE STRICT;
GRANT EXECUTE ON FUNCTION jsonb_merge(jsonb, jsonb) TO public;
CREATE OPERATOR || ( LEFTARG = jsonb, RIGHTARG = jsonb, PROCEDURE = jsonb_merge );
select * from pg_settings where name = 'deadlock_timeout';
begin;
create temp table a2(data jsonb);
insert into a2 values('{
    "key0": {
        "key01": "2018-05-06T12:36:11.916761+00:00",
        "key02": "DEFAULT_WEB_CONFIGURATION",
    "key1": {
        "key11": "Data System",
        "key12": "<p>Health,<p>my address<p>USA",
        "key13": "*Please refer to main screen labeling"
    }
}}'::jsonb);
commit;

嵌套的jsonb结构更新。可应用于删除。

update a2 set data =
    data::jsonb #-  '{key0, key1, key13}'
        || '{"key13":"screen labeling"}'::jsonb
returning *;

在@pozs回答的基础上,这里有两个可能对一些人有用的PostgreSQL函数。(需要PostgreSQL 9.3+)

按键删除:按键从JSON结构中删除一个值。

CREATE OR REPLACE FUNCTION "json_object_del_key"(
  "json"          json,
  "key_to_del"    TEXT
)
  RETURNS json
  LANGUAGE sql
  IMMUTABLE
  STRICT
AS $function$
SELECT CASE
  WHEN ("json" -> "key_to_del") IS NULL THEN "json"
  ELSE (SELECT concat('{', string_agg(to_json("key") || ':' || "value", ','), '}')
          FROM (SELECT *
                  FROM json_each("json")
                 WHERE "key" <> "key_to_del"
               ) AS "fields")::json
END
$function$;

按键递归删除:按键路径从JSON结构中删除一个值。(需要@pozs的json_object_set_key函数)

CREATE OR REPLACE FUNCTION "json_object_del_path"(
  "json"          json,
  "key_path"      TEXT[]
)
  RETURNS json
  LANGUAGE sql
  IMMUTABLE
  STRICT
AS $function$
SELECT CASE
  WHEN ("json" -> "key_path"[l] ) IS NULL THEN "json"
  ELSE
     CASE COALESCE(array_length("key_path", 1), 0)
         WHEN 0 THEN "json"
         WHEN 1 THEN "json_object_del_key"("json", "key_path"[l])
         ELSE "json_object_set_key"(
           "json",
           "key_path"[l],
           "json_object_del_path"(
             COALESCE(NULLIF(("json" -> "key_path"[l])::text, 'null'), '{}')::json,
             "key_path"[l+1:u]
           )
         )
       END
    END
  FROM array_lower("key_path", 1) l,
       array_upper("key_path", 1) u
$function$;

使用例子:

s1=# SELECT json_object_del_key ('{"hello":[7,3,1],"foo":{"mofu":"fuwa", "moe":"kyun"}}',
                                 'foo'),
            json_object_del_path('{"hello":[7,3,1],"foo":{"mofu":"fuwa", "moe":"kyun"}}',
                                 '{"foo","moe"}');

 json_object_del_key |          json_object_del_path
---------------------+-----------------------------------------
 {"hello":[7,3,1]}   | {"hello":[7,3,1],"foo":{"mofu":"fuwa"}}