运行 Android 中的 SQLite 查询

Question

我是 android 中 SQLite 查询的新手。正在尝试运行查询。但是，应用程序不断崩溃并出现以下错误：

Caused by: java.lang.IllegalStateException: Couldn't read row 1, col -1 from CursorWindow. Make sure the Cursor is initialized correctly before accessing data from it.

以下为代码摘录

public String getOutputData(){
    String inputData = "'Vineet'";

    Cursor cursorNew = db.rawQuery("SELECT email FROM groupseries INNER JOIN email " +
            "ON groupseries.emailid = email._id INNER JOIN user ON " +
            "groupseries.userid = user._id WHERE name=" + inputData, null);
    cursorNew.moveToFirst ();
    StringBuffer buffer = new StringBuffer();

    while(cursorNew.moveToNext()){
        int index1 = cursorNew.getColumnIndex(DatabaseHelper.KEY_NAME);
        int index2 = cursorNew.getColumnIndex(DatabaseHelper.KEY_EMAIL);
        String userID = cursorNew.getString(index1);
        String emailID = cursorNew.getString(index2);
        buffer.append(userID + " " + emailID + "\n");
    }
    return buffer.toString();
}

下面是我正在使用的 table 创建代码。（欢迎提出建议，使它不那么笨拙）。

private static final String DATABASE_NAME = "tryDemoDataBase.db";
    private static final String TABLE_NAME_USER = "user";
    private static final String TABLE_NAME_EMAIL = "email";
    private static final String TABLE_NAME_GROUP = "groupseries";
    private static final int DATABASE_VERSION = 12;
    private static final String KEY_ROWID_USER = "_id";
    private static final String KEY_ROWID_EMAIL = "_id";
    private static final String KEY_ROWID_GROUP = "_id";
    private static final String REFERENCE_USER_ID = "userid";
    private static final String REFERENCE_EMAIL_ID = "emailid";
    private static final String KEY_NAME="name";
    private static final String KEY_EMAIL = "email";
    private static final String CREATE_TABLE_USER = "create table "+ TABLE_NAME_USER
            + " ("+ KEY_ROWID_USER+" integer primary key autoincrement, "
            + KEY_NAME + " text)";
    private static final String CREATE_TABLE_EMAIL = "create table "+ TABLE_NAME_EMAIL
            + " ("+ KEY_ROWID_EMAIL+" integer primary key autoincrement, "
            + KEY_EMAIL + " text)";
    private static final String CREATE_TABLE_GROUP = "create table " + TABLE_NAME_GROUP+ " ("
            + KEY_ROWID_GROUP+" integer primary key autoincrement, "
            + REFERENCE_USER_ID + " integer, " + REFERENCE_EMAIL_ID + " integer)";

Answer 1

首先删除这一行：

cursorNew.moveToFirst();

因为你以后使用：

while (cursorNew.moveToNext())

所以实际上您跳过了结果的第一行（也许是唯一的一行）。
然后，如果要从 Cursor 对象中检索列 name，则必须在所选列中包含该列：

Cursor cursorNew = db.rawQuery("SELECT name, email FROM groupseries INNER JOIN email " +
            "ON groupseries.emailid = email._id INNER JOIN user ON " +
            "groupseries.userid = user._id WHERE name=" + inputData, null);

并建议使用推荐的安全方式将参数传递给查询，而不是直接连接它们。
使用 ? 占位符：

String inputData = "Vineet"; // no quotes
Cursor cursorNew = db.rawQuery(
            "SELECT name, email FROM groupseries INNER JOIN email " +
            "ON groupseries.emailid = email._id INNER JOIN user ON " +
            "groupseries.userid = user._id WHERE name=?", 
             new String[] {inputData}
);

运行 Android 中的 SQLite 查询

Running SQLite query in Android

java

android

sqlite

cursor

android-sqlite