android-sqlite

问题 hi have a two table one table contain column named Table A _id, Eng, Hindi other table contain Table B _id, Eng, Hindi i want to join two table by matching word with Eng if Eng word is not match it will be added into Table A which is from Table B otherwise Table A's value will be remain for example Now Table B Table A The Result would be on TABLE A is 回答1: FULL JOIN is a term to combine rows from multiple table. Does not apply to your needs. You only need to insert into table a all entries in

问题 I have been trying to export the SQLite database column values to a log.csv file. So far I have come to a point where, file is exported however without any kind of data. After the method is executed I recieve a java.lang.NullPointerException on a row where rawQuery is executed. Can somebody please assist me on this matter. thank you for your time, view, and answer on this issue in advance. Code for database: public class happinessDb extends SQLiteOpenHelper { public static final String KEY

问题 I have old project with Pre-loaded database in Assets folder. The project have SQLiteOpenHelper implemented for database operations. But now to update app I want to move my project to Room database library. So my question is, Is there any method or feature available in Room library with I can use preloaded db file in app at runtime. Or Is any way I can load db first and then from Room library I can directly execute queries on that db? 回答1: Is there any method or feature available in Room

问题 How can I associate two tables so that I can create a database that sort of matches the image attached. I understand that the experiment ID, Date, Name has to be part of the parent table, with the Trial #, Variable, and Result be the child table associated to the parent table. However, I'm not very sure how to implement this in Room Database persistence using Entity and Dao. Can someone show me how? I want the results to be that if the user selects the experiment in a recyclerview, it will be

问题 I have a room database . I have a column for date and it's saved as string . I used this query for sort my column : @Query("SELECT * FROM session WHERE class_id = :classId ORDER BY session_date ASC") List<SessionEntry> getAllSessions(int classId); Result : 1398/11/25 1398/11/29 1398/12/5 1398/2/14 1398/4/25 1398/6/17 1398/6/30 1398/7/9 1398/9/14 but i want to sort like this : 1398/2/14 1398/4/25 1398/6/17 1398/6/30 1398/7/9 1398/9/14 1398/11/25 1398/11/29 1398/12/5 Is there any way I could

问题 I'm trying to select some data from database and I have two slices of code to do it: cursor = builder.query(db, new String[]{"col1", "col2", "col3"}, "id = ?", new String[]{getSID(db)}, null, null, null); and cursor = builder.query(db, new String[]{"col1", "col2", "col3"}, "id = " + getSID(db), null, null, null, null); The difference between them is that first one seems to be more correct according to documentation, but it also doesn't work - cursor is empty. Instead of the second one - I'm

问题 I have created a trivia quiz for android devices. I have a database with questions in assets folder and dbHelper class. Everything works fine, but now i want to fix some typos and add more questions. I need to update database, but i don't know how to do that. I found this dbHelper class on the Internet and i don't have enough knowledge to to this by myself. I understand that I should compare versions of new database and existing database and if they don't match I need to remove old database

问题 I have a SQLite database powering all the content in an Android app. I have a DatabaseHelper class that extends SQLiteAssetHelper. I have been having problems with too many instances of my database and then getting a SQLiteCantOpenDatabaseException. To counter this, I have changed my class to maintain a single instance of the DatabaseHelper object. I have the following: private static DatabaseHelper databaseHelper; public static synchronized DatabaseHelper getInstance(Context context, boolean

问题 I am trying to create multiple databases at runtime. The user enter the database name and the system must create it. here is my code First.Java public class First extends Activity implements OnClickListener { Button btnOk; EditText inputName; DatabaseHandler db = null; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.db); try { this.getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN);

问题 I have been trying to use SQLite database for storing data in Android application. The database is used to store data for a chat application and also to store various states of the messages like sent, delivered, read etc. The problem I am facing in Android is that the queries are running without error but when I try to insert the value using the saveChatMessage function below it always returns rowID = 1 . There are no errors thrown from database, but when I try to call getAllUnsentMessages ,