SQlite - Android - 外键语法 [英] SQlite - Android - Foreign key syntax

问题描述

我一直在尝试让外键在我的 Android SQLite 数据库中工作.我尝试了以下语法，但它给了我一个强制关闭:

I've been trying to get foreign keys working within my Android SQLite database. I have tried the following syntax but it gives me a force close:

private static final String TASK_TABLE_CREATE = "create table "
            + TASK_TABLE + " (" + TASK_ID
            + " integer primary key autoincrement, " + TASK_TITLE
            + " text not null, " + TASK_NOTES + " text not null, "
    + TASK_DATE_TIME + " text not null, FOREIGN KEY ("+TASK_CAT+") REFERENCES "+CAT_TABLE+" ("+CAT_ID+"));";

任何想法我可能做错了什么?如果您需要查看其他表结构，那么我可以，它只是一个非常简单的结构，用于带有 ID 和名称的第二个.

Any ideas what I might be doing wrong? if you need to see the other table structure then I can, its just a very simple structure for the second with an ID and a name.

这是错误:

03-13 13:42:35.389:错误/AndroidRuntime(312):由以下原因引起:android.database.sqlite.SQLiteException:国外未知列taskCat"关键定义:创建表提醒(_id 整数主键自动增量，task_title 文本不是null，注释文本不为空，提醒日期时间文本不为空，外键(taskCat)参考类别 (_id));

03-13 13:42:35.389: ERROR/AndroidRuntime(312): Caused by: android.database.sqlite.SQLiteException: unknown column "taskCat" in foreign key definition: create table reminders (_id integer primary key autoincrement, task_title text not null, notes text not null, reminder_date_time text not null, FOREIGN KEY (taskCat) REFERENCES category (_id));

推荐答案

你必须先定义你的 TASK_CAT 列，然后在上面设置外键.

You have to define your TASK_CAT column first and then set foreign key on it.

private static final String TASK_TABLE_CREATE = "create table "
        + TASK_TABLE + " (" 
        + TASK_ID + " integer primary key autoincrement, " 
        + TASK_TITLE + " text not null, " 
        + TASK_NOTES + " text not null, "
        + TASK_DATE_TIME + " text not null,"
        + TASK_CAT + " integer,"
        + " FOREIGN KEY ("+TASK_CAT+") REFERENCES "+CAT_TABLE+"("+CAT_ID+"));";

您可以在 sqlite 外键 doc 上找到更多信息.

More information you can find on sqlite foreign keys doc.

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