PostgreSQL中不存在的地方給出語法錯誤

Question

當試圖使用WHERE NOT EXISTS子句來防止在列age中添加具有重複值的行時，我得到錯誤syntax error at or near "WHERE"。

它爲什麼會拋出語法錯誤？我正在使用Postgresql 9.1。

SQL

INSERT INTO live.users ("website", "age") 
values ('abc', '123') 
WHERE NOT EXISTS (SELECT age FROM live.users WHERE age = 123); 

錯誤

ERROR: syntax error at or near "WHERE" 
LINE 6: WHERE NOT EXISTS (SELECT age FROM live.users W... 

Answer 1

做，而不是：

INSERT INTO live.users ("website", "age") 
SELECT 'abc', 123 
WHERE NOT EXISTS (SELECT age FROM live.users WHERE age = 123); 

Answer 2

INSERT INTO live.users ("website", "age") 
select 'abc', '123' 
WHERE NOT EXISTS (SELECT age FROM live.users WHERE age = 123); 

Answer 3

我encountere d在PLPGSQL中使用WHERE field NOT EXISTS時遇到的一些問題。相反，運行良好的是WHERE field NOT IN，使用後我沒有收到功能錯誤。

Answer 4

我看你問V9.1，但它已經4年以來到現在，從PostgreSQL v9.5 - INSERT開始給你ON CONFLICT … DO NOTHING選項：

INSERT INTO live.users("website", "age") VALUES('abc', '123') ON CONFLICT ("age") DO NOTHING 

值得注意這需要建立在目標表上相應的約束 - 但在大多數情況下，我想你會擁有它。否則，您將得到：

ERROR: there is no unique or exclusion constraint matching the ON CONFLICT specification