发生冲突的 Postgres 会更新复合主键

Question

我有一个 table 用户回答问题的地方。规则是用户可以回答许多问题，或者许多用户可以回答一个问题，但一个用户只能回答一个特定问题一次。如果用户再次回答这个问题，它应该简单地替换旧的。通常，当我们处理唯一列时，on conflict do update 起作用。在这种情况下，列 person_id 和 question_id 不能是唯一的。然而，两者的结合总是独一无二的。如何实现冲突更新的插入语句？

CREATE TABLE "answer" (
  "person_id" integer NOT NULL REFERENCES person(id), 
  "question_id" integer NOT NULL REFERENCES question(id) ON DELETE CASCADE, /* INDEXED */
  "answer" character varying (1200) NULL,
  PRIMARY KEY (person_id, question_id) 
);

Answer 1

只需将两个键都放在 ON CONFLICT 子句中：

INSERT INTO answer VALUES (1,1,'q1') 
ON CONFLICT (person_id,question_id) 
DO UPDATE SET answer = EXCLUDED.answer;

示例：

INSERT INTO answer VALUES (1,1,'q1') 
ON CONFLICT (person_id,question_id) 
DO UPDATE SET answer = EXCLUDED.answer;             

SELECT * FROM answer;
 person_id | question_id | answer 
-----------+-------------+--------
         1 |           1 | q1
(1 Zeile)

INSERT INTO answer VALUES (1,1,'q1-UPDATED') 
ON CONFLICT (person_id,question_id) 
DO UPDATE SET answer = EXCLUDED.answer;             

SELECT * FROM answer;
 person_id | question_id |   answer   
-----------+-------------+------------
         1 |           1 | q1-UPDATED
(1 Zeile)

演示：db<>fiddle

Answer 2

您还可以在 table 的外部定义主要的，这样您就不需要重写其中包含的所有列。

CREATE TABLE "answer" (
  "person_id" integer NOT NULL REFERENCES person(id), 
  "question_id" integer NOT NULL REFERENCES question(id) ON DELETE CASCADE, /* INDEXED */
  "answer" character varying (1200) NULL);

ALTER TABLE "answer" ADD CONSTRAINT answer_pk PRIMARY KEY (person_id, question_id);

然后：

INSERT INTO answer VALUES (1,1,'q1') ON CONFLICT ON CONSTRAINT answer_pk DO UPDATE SET answer = EXCLUDED.answer;

将来约束发生变化时，您无需手动调整插入语句来反映这一点。

发生冲突的 Postgres 会更新复合主键

Postgres on conflict do update on composite primary keys

sql

postgresql

upsert