Question

我正在尝试在CTE返回 ~~null~~ false时插入一行，但是我不知道该怎么做

不工作：

with cte as (SELECT EXISTS (SELECT * FROM commentsvoted WHERE id = $1 AND user_id = $2))
INSERT INTO commentsvoted = 
(CASE WHEN cte.exists IS FALSE (id, user_id, votes, thread_id) VALUES($1, 
$2, true, $3)
ELSE commentsvoted
END)

我的cte：

with cte as (SELECT EXISTS (SELECT * FROM commentsvoted WHERE id = $1 AND user_id = $2))

当大小写为 ~~null~~ false时我想插入的内容：

INSERT INTO commentsvoted(id, user_id, votes, thread_id) VALUES($1, $2, true, $3)

Answer 1

我想这就是你想要的：

WITH cte as (
      SELECT EXISTS (SELECT * FROM commentsvoted WHERE id = $1 AND user_id = $2) as flag
     )
INSERT INTO commentsvoted (id, user_id, votes, thread_id)  
   SELECT $1, $2, true, $3
   FROM cte
   WHERE NOT FLAG;

CTE将不包含NULL，因为EXISTS返回true或false。

我的意思是，这就是您想要的。您可能只希望在表上具有唯一索引：

create unique index unq_commentsvoted_id_user_id on commentsvoted(id, user_id);

然后数据库将阻止您插入重复的值。

Postgres-在以下情况下插入并使用案例

1 个答案: