“如果不存在则插入”语句在SQLite [英] "Insert if not exists" statement in SQLite

问题描述

我有一个sqlite数据库。我试图在表书签中插入值（users_id，lessoninfo_id），前提是它们在一行中不存在。

I have a sqlite database. I am trying to insert values(users_id,lessoninfo_id) in table bookmarks, only if both do not exists before in a row.

INSERT INTO bookmarks(users_id,lessoninfo_id) 
VALUES(
    (SELECT _id FROM Users WHERE User='"+$('#user_lesson').html()+"'),
        (SELECT _id FROM lessoninfo 
        WHERE Lesson="+lesson_no+" AND cast(starttime AS int)="+Math.floor(result_set.rows.item(markerCount-1).starttime)+") 
        WHERE NOT EXISTS (
            SELECT users_id,lessoninfo_id from bookmarks 
            WHERE users_id=(SELECT _id FROM Users 
            WHERE User='"+$('#user_lesson').html()+"') AND lessoninfo_id=(
                SELECT _id FROM lessoninfo
                WHERE Lesson="+lesson_no+")))

这会给出错误，说明在附近的语法的db错误。

This gives error saying db error near where syntax.

推荐答案

如果你有一个名为memos的表有两个 id 和 text 列应该能够这样做：

If you have a table called memos that has two columns id and text you should be able to do like this:

INSERT INTO memos(id,text) 
SELECT 5, 'text to insert' 
WHERE NOT EXISTS(SELECT 1 FROM memos WHERE id = 5 AND text = 'text to insert');

如果记录已包含 text 等于'要插入的文本'， id 等于5，则插入操作将被忽略。

If a record already contains a row where text is equal to 'text to insert' and id is equal to 5, then the insert operation will be ignored.

我不知道这是否会为你的特定查询工作，但也许它给你一个提示如何继续。

I don't know if this will work for your particular query, but perhaps it give you a hint on how to proceed.

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