怎么使用PostgreSQL的SQL/JSON函数

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PostgreSQL 12提供了SQL/JSON函数用以兼容SQL 2016 SQL/JSON特性.
这些函数包括:

[local]:5432 pg12@testdb=# \df jsonb_path*                                                                     List of functions   Schema   |          Name          | Result data type |                                    Argument data types                                    | Type ------------+------------------------+------------------+-------------------------------------------------------------------------------------------+------ pg_catalog | jsonb_path_exists      | boolean          | target jsonb, path jsonpath, vars jsonb DEFAULT '{}'::jsonb, silent boolean DEFAULT false | func pg_catalog | jsonb_path_exists_opr  | boolean          | jsonb, jsonpath                                                                           | func pg_catalog | jsonb_path_match       | boolean          | target jsonb, path jsonpath, vars jsonb DEFAULT '{}'::jsonb, silent boolean DEFAULT false | func pg_catalog | jsonb_path_match_opr   | boolean          | jsonb, jsonpath                                                                           | func pg_catalog | jsonb_path_query       | SETOF jsonb      | target jsonb, path jsonpath, vars jsonb DEFAULT '{}'::jsonb, silent boolean DEFAULT false | func pg_catalog | jsonb_path_query_array | jsonb            | target jsonb, path jsonpath, vars jsonb DEFAULT '{}'::jsonb, silent boolean DEFAULT false | func pg_catalog | jsonb_path_query_first | jsonb            | target jsonb, path jsonpath, vars jsonb DEFAULT '{}'::jsonb, silent boolean DEFAULT false | func(7 rows)

简单试用:

[local]:5432 pg12@testdb=# CREATE TABLE characters (data jsonb);         "weight" : 0.1       },       {"name" : "ring of strength",        "weight" : 2.4       }     ],     "arm_right" : "Sword of flame",     "arm_left" : "Shield of faith"   }}');CREATE TABLETime: 208.690 ms[local]:5432 pg12@testdb=# INSERT INTO characters VALUES ('pg12@testdb'# { "name" : "Yksdargortso",pg12@testdb'#   "id" : 1,pg12@testdb'#   "sex" : "male",pg12@testdb'#   "hp" : 300,pg12@testdb'#   "level" : 10,pg12@testdb'#   "class" : "warrior",pg12@testdb'#   "equipment" :pg12@testdb'#    {pg12@testdb'#      "rings" : [pg12@testdb'#        { "name" : "ring of despair",pg12@testdb'#          "weight" : 0.1pg12@testdb'#        },pg12@testdb'#        {"name" : "ring of strength",pg12@testdb'#         "weight" : 2.4pg12@testdb'#        }pg12@testdb'#      ],pg12@testdb'#      "arm_right" : "Sword of flame",pg12@testdb'#      "arm_left" : "Shield of faith"pg12@testdb'#    }pg12@testdb'# }');INSERT 0 1Time: 3.881 ms[local]:5432 pg12@testdb=# [local]:5432 pg12@testdb=# [local]:5432 pg12@testdb=# SELECT jsonb_path_query(data, '$.equipment.rings[0].name') AS ring_name FROM characters;     ring_name     ------------------- "ring of despair"(1 row)Time: 10.081 ms[local]:5432 pg12@testdb=# SELECT jsonb_path_query(data, '$.equipment.rings[0].*') AS data FROM characters;       data        ------------------- "ring of despair" 0.1(2 rows)Time: 0.687 ms[local]:5432 pg12@testdb=# SELECT jsonb_path_query(data, '$.equipment.rings[*].weight.floor()') AS weight FROM characters; weight -------- 0 2(2 rows)

如果是PG 11或以下版本,则需要使用#>>等操作符实现

testdb=# select data#>>'{equipment,rings,0,name}' AS ring_name FROM characters;    ring_name    ----------------- ring of despair(1 row)

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