我是 Android 开发新手，正在从事一个需要数据库交互的项目 当尝试使用 sqlite 中的邻接模型创建表但编译失败并显示此错误消息时
| id | parentid | name |
-----------------------------------------
| 1 | null | animal |
| 2 | null |vegetable |
| 3 | 1 | doggie |
| 4 | 2 | carrot |
| | | |
| | | |
这是我的代码:
private static final String CREATE_TABLE_CATEGORIES="CREATE TABLE "+TABLE_CATEGORIES+"(id INTEGER PRIMARY KEY AUTOINCREMENT,"+category_name+
" TEXT,parentid INTEGER ,foreign key parentid_fk(parentid) references "+TABLE_CATEGORIES+" (id));";
@Override
public void onCreate(SQLiteDatabase db){
//Creation required tables
db.execSQL(CREATE_TABLE_CATEGORIES);
}
....
....
....
....
@Override
public void onUpgrade(SQLiteDatabase db,int oldVersion,int newVersion){
// on upgrade drop older tables
db.execSQL("PRAGMA foreign_keys = ON;");
db.execSQL("DROP TABLE IF EXISTS " + CREATE_TABLE_CATEGORIES);
// create new tables
onCreate(db);
}
这是错误:
at dalvik.system.NativeStart.main(Native Method)
Caused by: android.database.sqlite.SQLiteException: near "parentid_fk": syntax error (code 1): , while compiling: CREATE TABLE Categories(id INTEGER PRIMARY KEY AUTOINCREMENT,name TEXT,parentid INTEGER ,foreign key parentid_fk(parentid) references Categories (id));
最佳答案
要为外键约束命名，必须使用 CONSTRAINT 关键字:
CONSTRAINT parentid_fk FOREIGN KEY (parentid) REFERENCES Categories(id)
或者，不要给它命名:
FOREIGN KEY (parentid) REFERENCES Categories(id)
关于java - Android sqlite邻接模型，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/25549378/