Postgresql插入選擇多行

Question

我正在創建一個過程來解析輸入json數據並存儲在表中。該功能看起來像：

create or replace function test_func(d json) 
returns void as $$ 
    begin 
    with n as (
    insert into t1 (name) values (d::json -> 'name') returning id 
    ), c as (
    insert into t2 (cars) values json_array_elements_text(d::json -> 'cars') returning id 
    ) 
    insert into t3 (id, name_id, cars_id, brand) 
    select 1, n.id, c.id, json_array_elements_text(d::json -> 'brands') from n, c; 
end; 
$$ language plpgsql; 


CREATE TABLE t1 
(
    "id" SERIAL PRIMARY KEY, 
    "name" text NOT NULL 
) 

CREATE TABLE t2 
(
    "id" SERIAL PRIMARY KEY, 
    "cars" text NOT NULL, 
    "car_type" int 
) 

CREATE TABLE t3 
(
    "id" int, 
    "name_id" int REFERENCES t1(id), 
    "cars_id" int REFERENCES t2(id), 
    "brand" text 
) 

數據輸入名稱爲文本，汽車和品牌是數組，都包裹在一個JSON中。 所以最後一個插入有混合值類型，如果人有兩輛車，我有4行插入t3因爲c.id和json_array_elements_text（d :: json - >'品牌'）都有兩個數據集，2x2 = 4 ，如何將插入的值映射到一個？所以第一個c.id應該映射到第一個品牌。

Answer 1

要映射它們，你必須加入不是真實的，但在不同的行。

這裏是示例如何加入兩個ID with ordinality - 希望它會有所幫助。根據您的JSON樣本

t=# with j as (select '{"name":"john", "cars":["bmw X5 xdrive","volvo v90 rdesign"], "brands":["bmw","volvo"]}'::json d) 
select car,brand,t1.id from j 
join json_array_elements_text(j.d->'cars') with ordinality t1(car,id) on true 
join json_array_elements_text(j.d->'brands') with ordinality t2(brand,id) on t1.id = t2.id 
; 
     car  | brand | id 
-------------------+-------+---- 
bmw X5 xdrive  | bmw | 1 
volvo v90 rdesign | volvo | 2 
(2 rows) 

更新闡述了OP：

可以避開映射多行，通過聚合EM，然後利用指數：

您的FN：

create or replace function test_func(d json) 
returns void as $$ 
    begin 
with j as (select d) 
, a as (
    select car,brand,t1.id oid 
    from j 
    join json_array_elements_text(j.d->'cars') with ordinality t1(car,id) on true 
    join json_array_elements_text(j.d->'brands') with ordinality t2(brand,id) on t1.id = t2.id 
) 
, n as (
    insert into t1 (name) values (d::json -> 'name') returning id 
), c as (
    insert into t2 (cars) select car from a order by oid returning id 
) 
, ag as (
    select array_agg(c.id) cid from c 
) 
insert into t3 (id, name_id, cars_id, brand) 
    select 1, n.id,cid[oid], brand 
    from a 
    join n on true 
    join ag on true 
; 
end; 
$$ language plpgsql; 

您的表格：

CREATE TABLE t1 ("id" SERIAL PRIMARY KEY, "name" text NOT NULL); 
CREATE TABLE t2 ("id" SERIAL PRIMARY KEY, "cars" text NOT NULL); 
CREATE TABLE t3 ("id" int, "name_id" int REFERENCES t1(id), "cars_id" int REFERENCES t2(id), "brand" text); 

執行：

t=# select test_func('{"name":"john", "cars":["bmw X5 xdrive","volvo v90 rdesign"], "brands":["bmw","volvo"]}'); 
test_func 
----------- 

(1 row) 

t=# select * from t1; 
id | name 
----+-------- 
14 | "john" 
(1 row) 

t=# select * from t2; 
id |  cars 
----+------------------- 
27 | bmw X5 xdrive 
28 | volvo v90 rdesign 
(2 rows) 

t=# select * from t3; 
id | name_id | cars_id | brand 
----+---------+---------+------- 
    1 |  14 |  27 | bmw 
    1 |  14 |  28 | volvo 
(2 rows)