Question

如果行存在，如何检查sqlite db？我在实现sqlite db时的风格是这样的

public class EmployeeDBController extends SQLiteOpenHelper {

    public EmployeeDBController(Context applicationcontext) {
        super(applicationcontext, "registeruser.db", null, 1);

    }

    public  SQLiteDatabase db;
    //Creates Table
    @Override
    public void onCreate(SQLiteDatabase database) {
        String query;
        query = "CREATE TABLE register ( userId INTEGER PRIMARY KEY, Name text, Age text, Gender text," +
                "HomeAddress text, Password text, QRID text, udpateStatus TEXT)";
        database.execSQL(query);
    }
    @Override
    public void onUpgrade(SQLiteDatabase database, int version_old, int current_version) {
        String query;
        query = "DROP TABLE IF EXISTS register";
        database.execSQL(query);
        onCreate(database);
    }
}

例如：我想检查sqlite db中是否存在“john”的“Name”。

Answer 1

有一个helper function可以避免不得不用光标捣乱：

public boolean rowExists(String table, String column, String value) {
    long count = DatabaseUtils.queryNumEntries(db,
            table, column+" = ?", new String[]{ value });
    return count > 0;
}

Answer 2

使用此方法！

public boolean isRowExist(/*YOUR_INPUTS*/){
    try {
        db = mDBHelper.getReadableDatabase();
        String selectQuery =  YOUR_SEARCH_QUERY_STATMENT
         //You should use YOUR_INPUTS to create a selectQuery that can select the row/rows for you

        Cursor c = db.rawQuery(selectQuery, null);
        if(c.getCount()>=1){
            c.close();
            return true;
        }
        c.close();
        return false;
    } catch (Exception e) {
        return false;
    }
}

检查这种实现sqlite db是否存在行

2 个答案: