KingbaseES Json 系列七–Json记录操作函数二
(JSONB_POPULATE_RECORD,JSONB_POPULATE_RECORDSET,JSON_POPULATE_RECORD,JSON_POPULATE_RECORDSET)
JSON 数据类型是用来存储 JSON(JavaScript Object Notation)数据的。KingbaseES为存储JSON数据提供了两种类型:JSON和 JSONB。JSON 和 JSONB 几乎接受完全相同的值集合作为输入。
本文将主要介绍Kingbase数据库的Json记录操作函数第二部分。
准备数据：
CREATE TABLE "public"."jsontable" (
"id" integer NULL,
"jsondata" json NULL,
"jsonvarchar" varchar NULL,
"jsonarray" json NULL,
"jsonrecord" json NULL,
"jsonset" json NULL
);
INSERT INTO "public"."jsontable" ("id","jsondata","jsonvarchar","jsonarray","jsonrecord","jsonset") VALUES
(1,'{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}','{"f2": {"f3": 1}, "f4": {"f5": 99, "f6": "foo"}}','[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false,"stringy"]','{"a":1,"b":"bcol","c":"cc"}','[{"a":1,"b":"bcol","c":"cc"},{"a":1,"b":"bcol","d":""}]'),
(2,'{"a":[1,2,3,4,5]}','{"a": [1, 2, 3, 4, 5]}','[1,2,3,4,5]','{"a":1,"b":"bcol","c":""}','[{"a":1,"b":"bcol","c":""},{"a":1,"b":"bcol","e":""}]'),
(3,'{"a":1, "b": ["2", "a b"],"c": {"d":4, "e": "ab c"}}','{"a": 1, "b": ["2", "a b"], "c": {"d": 4, "e": "ab c"}}','[{"f1":1,"f2":null},2,null,3]','{"a":1,"b":"bcol","d":"dd"}','[{"a":1,"b":"bcol","c":"cc_3_1"},{"a":1,"b":"bcol","c":"cc_3_2"}]');
json函数列表
json函数简介
JSONB_POPULATE_RECORD
功能：
JSON函数，扩展 from_json 中的对象成一个行，它的列匹配由 base 定义的记录类型。在 JSONB 对象的那些与自定义类型中的列名匹配的字段，他们的值将被插入到对应的输出的列中。而 JSONB 对象中的那些没有匹配到自定类型中的列名的字段将会被忽略。
用法：
jsonb_populate_record(base anyelement,from_json jsonb)
示例：
-- 创建自定义的 SQL 类型 CREATE TYPE recordtype as (a INT, b text, c text);
--解析json数据 demo=# SELECT * FROM jsonb_populate_record(NULL::recordtype , '{"a":1,"b":"bcol","c":"c_text"}'); a | b | c ---+------+-------- 1 | bcol | c_text (1 行记录) -- 数据value的类型需要能够隐式转换到record的匹配类型中 demo=# SELECT * FROM jsonb_populate_record(NULL::recordtype , '{"a":"a","b":"bcol","c":""}'); 错误: 无效的类型 integer 输入语法: "a" demo=# SELECT * FROM jsonb_populate_record(NULL::recordtype , '{"a":"1","b":"bcol","c":""}'); a | b | c ---+------+--- 1 | bcol | (1 行记录) -- 数据中不存在record定义的属性时，默认返回null demo=# SELECT * FROM jsonb_populate_record(NULL::recordtype , '{"a":1,"b":"bcol"}'); a | b | c ---+------+--- 1 | bcol | (1 行记录) -- 数据中多余的属性时，默认忽略 demo=# SELECT * FROM jsonb_populate_record(NULL::recordtype , '{"a":1,"b":"bcol","c":"c_text","d":"dcol"}'); a | b | c ---+------+-------- 1 | bcol | c_text (1 行记录) -- 通过设置record转换类型，设置数据不存在时默认值 demo=# SELECT * FROM jsonb_populate_record((0 , 'b_default' , 'not exist' )::recordtype , '{"a":1,"b":"bcol"}'); a | b | c ---+------+----------- 1 | bcol | not exist (1 行记录) -- 从表字段中解析数据 demo=# SELECT jt.jsonrecord ,jpr.* FROM jsontable jt , jsonb_populate_record(NULL::recordtype , jt.jsonrecord) jpr; jsonrecord | a | b | c -----------------------------+---+------+---- {"a":1,"b":"bcol","c":"cc"} | 1 | bcol | cc {"a":1,"b":"bcol","c":""} | 1 | bcol | {"a":1,"b":"bcol","d":"dd"} | 1 | bcol | (3 行记录) -- 通过设置record转换类型，设置数据不存在时默认值 demo=# SELECT jt.jsonrecord ,jpr.* FROM jsontable jt , jsonb_populate_record((0 , 'not exist' , 'not exist')::recordtype , jt.jsonrecord) jpr; jsonrecord | a | b | c -----------------------------+---+------+----------- {"a":1,"b":"bcol","c":"cc"} | 1 | bcol | cc {"a":1,"b":"bcol","c":""} | 1 | bcol | {"a":1,"b":"bcol","d":"dd"} | 1 | bcol | not exist (3 行记录)
JSONB_POPULATE_RECORDSET
功能：
JSON函数，扩展 from_json 中最外层的对象数组成一个集合，它的列匹配由 base 定义的记录类型。
用法：
jsonb_populate_recordset(base anyelement,from_json jsonb)
示例：
CREATE TYPE recordtype as (a INT, b text, c text);
-- 直接解析json数据 demo=# SELECT * FROM jsonb_populate_recordset(NULL::recordtype , '[{"a":1,"b":"bcol","c":"cc"},{"a":1,"b":"bcol","c":"c_dd"}]'); a | b | c ---+------+------ 1 | bcol | cc 1 | bcol | c_dd (2 行记录) -- 数据value的类型需要能够隐式转换到record的匹配类型中 demo=# SELECT * FROM jsonb_populate_recordset(NULL::recordtype , '[{"a":"a","b":"bcol","c":"cc"},{"a":1,"b":"bcol","d":""}]'); 错误: 无效的类型 integer 输入语法: "a" demo=# SELECT * FROM jsonb_populate_recordset(NULL::recordtype , '[{"a":1,"b":"bcol","c":"cc"},{"a":1,"b":"bcol","d":""}]'); a | b | c ---+------+---- 1 | bcol | cc 1 | bcol | (2 行记录) -- 数据中不存在record定义的属性时，默认返回null -- 数据中多余的属性时，默认忽略 demo=# SELECT * FROM jsonb_populate_recordset(NULL::recordtype , '[{"a":1,"b":"bcol","c":"cc"},{"a":1,"b":"bcol","d":""}]'); a | b | c ---+------+---- 1 | bcol | cc 1 | bcol | (2 行记录) -- 通过设置record转换类型，设置数据不存在时默认值 demo=# SELECT * FROM jsonb_populate_recordset((0 , 'b_default' , 'not exist' )::recordtype , '[{"a":1,"b":"bcol","c":"cc"},{"a":1,"b":"bcol","d":""}]'); a | b | c ---+------+----------- 1 | bcol | cc 1 | bcol | not exist (2 行记录) -- 从表字段中解析数据 demo=# SELECT jt.jsonset ,jpr.* FROM jsontable jt , jsonb_populate_recordset(NULL::recordtype , jt.jsonset) jpr; jsonset | a | b | c -------------------------------------------------------------------+---+------+-------- [{"a":1,"b":"bcol","c":"cc"},{"a":1,"b":"bcol","d":""}] | 1 | bcol | cc [{"a":1,"b":"bcol","c":"cc"},{"a":1,"b":"bcol","d":""}] | 1 | bcol | [{"a":1,"b":"bcol","c":""},{"a":1,"b":"bcol","e":""}] | 1 | bcol | [{"a":1,"b":"bcol","c":""},{"a":1,"b":"bcol","e":""}] | 1 | bcol | [{"a":1,"b":"bcol","c":"cc_3_1"},{"a":1,"b":"bcol","c":"cc_3_2"}] | 1 | bcol | cc_3_1 [{"a":1,"b":"bcol","c":"cc_3_1"},{"a":1,"b":"bcol","c":"cc_3_2"}] | 1 | bcol | cc_3_2 (6 行记录) -- 通过设置record转换类型，设置数据不存在时默认值 demo=# SELECT jt.jsonset ,jpr.* FROM jsontable jt , jsonb_populate_recordset((0 , 'not exist' , 'not exist')::recordtype , jt.jsonset) jpr; jsonset | a | b | c -------------------------------------------------------------------+---+------+----------- [{"a":1,"b":"bcol","c":"cc"},{"a":1,"b":"bcol","d":""}] | 1 | bcol | cc [{"a":1,"b":"bcol","c":"cc"},{"a":1,"b":"bcol","d":""}] | 1 | bcol | not exist [{"a":1,"b":"bcol","c":""},{"a":1,"b":"bcol","e":""}] | 1 | bcol | [{"a":1,"b":"bcol","c":""},{"a":1,"b":"bcol","e":""}] | 1 | bcol | not exist [{"a":1,"b":"bcol","c":"cc_3_1"},{"a":1,"b":"bcol","c":"cc_3_2"}] | 1 | bcol | cc_3_1 [{"a":1,"b":"bcol","c":"cc_3_1"},{"a":1,"b":"bcol","c":"cc_3_2"}] | 1 | bcol | cc_3_2 (6 行记录)
JSON_POPULATE_RECORD
功能：
JSON函数，扩展 from_json 中的对象成一个行，它的列匹配由 base 定义的记录类型。
用法：
json_populate_record(base anyelement,from_json jsonb)
示例：
参照JSONB_POPULATE_RECORD使用示例
JSON_POPULATE_RECORDSET
功能：
JSON函数，扩展 from_json 中最外层的对象数组成一个集合，它的列匹配由 base 定义的记录类型。
用法：
json_populate_record(base anyelement,from_json jsonb)复制
示例：
参照JSONB_POPULATE_RECORDSET使用示例
