仅在满足特定条件时才执行insert语句

时间:2012-07-13 09:40:53

标签: sql postgresql

我想仅在满足某个条件时才运行insert语句。有没有办法在纯sql中做到这一点?

我想在pl / pgsql中做的一个例子:

CREATE OR REPLACE FUNCTION set_search_lock (
    userid     IN   integer,
)
    RETURNS boolean AS $body$


DECLARE
BEGIN

    PERFORM 'A' FROM LOCK_TABLE WHERE USERID = userid LIMIT 1;

    IF NOT FOUND THEN
        INSERT INTO LOCK_TABLE (USERID) VALUES (userid);
        RETURN true;
    ELSE
        RETURN false;
    END IF;


END;
$body$
LANGUAGE PLPGSQL;

1 个答案:

答案 0 :(得分:3)

假设您要插入值42,那么如果没有一行,则以下内容只会插入一行:

insert into lock_table (userid) 
select 42
where not exists (select 1 from lock_table where userid = 42);