sqlite

问题 I've been getting an inconsistent, non-reproducible crash upon users upgrading to a new version of the local SQLite DB when updating the app. Fatal Exception: android.database.sqlite.SQLiteException: duplicate column name: upload_pending (code 1): , while compiling: ALTER TABLE purchases ADD COLUMN upload_pending TINYINT DEFAULT 0 ################################################################# Error Code : 1 (SQLITE_ERROR) Caused By : SQL(query) error or missing database. (duplicate column

问题 Over the past days I have been getting comfortable with Android Architecture Components and I've been mostly interested in the Paging Library for handling and displaying lists of data from a remote source. For the best UX it is better to load data first into the database, in this case Room then display it in a recyclerview using the pagingLibrary and adapters. My concern is this, lets say an api has 1000s of records or a twitter feed even and all this data has to pass through the db then to

问题 Over the past days I have been getting comfortable with Android Architecture Components and I've been mostly interested in the Paging Library for handling and displaying lists of data from a remote source. For the best UX it is better to load data first into the database, in this case Room then display it in a recyclerview using the pagingLibrary and adapters. My concern is this, lets say an api has 1000s of records or a twitter feed even and all this data has to pass through the db then to

问题 This question already has answers here : What is a NullPointerException, and how do I fix it? (12 answers) Closed 4 years ago . I have an activity in which i am trying to get the list of data based on some condition . This selectsome() function is in the SQLiteOpenHelper subclass. MyDBHandler dbhelper = new MyDBHandler(this); Cursor cursor; cursor = dbhelper.selectSome(value); In class MyDBHelper.java public Cursor selectSome(String arg) { String columns[]=new String[]{"_id","_hotelname","

问题 I am migrating my old Android project to new standards, I got stuck in between room database , not able to find how to execute these 2 SQLite commands using room database . I have 2 queries which are working in a nested manner, so to achieve the same result using room is there any possibility. default public ArrayList getOfflineRoomsAndObjectsByParentIds(String parentId, String site_id, Context context) { databaseHandler = new DatabaseHandler(context); Cursor cr = null; ArrayList<Room>

问题 I'm building an Android app, which should: show some data, loaded from a server in the Internet. At the moment I have a local SQliteDB used in my app where the data is stored, which should be displayed. I use this, because I want to be able to show the data, even if there is temporarily no internet connection available. Next step I will work on inserting data in the local SQliteDB from a internet server. I thought about doing it this way: When app starts, check if internet is available. If

问题 I know from this question that Firefox 3.0 and up stores its cookies in an SQLite database. My question is: can you access this database from other desktop programs in such a way that you could add a cookie? I realize this has security implications. However, I do not want to read them at all. I want to be able to set one cookie if possible. I don't even want to overwrite a cookie. I just want to add it if it isn't there already. This is sort of a personal project I'm working on for fun. This

问题 I have created a script that finds the last value in the first row of my database import sqlite3 global SerialNum conn = sqlite3.connect("MyFirstDB.db") conn.text_factory = str c = conn.cursor() SerialNum = c.execute('select Serial from BI4000 where Serial in (Select max(Serial) from BI4000)') print SerialNum conn.commtt() conn.close() the program prints the result [('00003',)] which is the last result in the current database, all the data that will be entered into the final database will be

问题 I have created a script that finds the last value in the first row of my database import sqlite3 global SerialNum conn = sqlite3.connect("MyFirstDB.db") conn.text_factory = str c = conn.cursor() SerialNum = c.execute('select Serial from BI4000 where Serial in (Select max(Serial) from BI4000)') print SerialNum conn.commtt() conn.close() the program prints the result [('00003',)] which is the last result in the current database, all the data that will be entered into the final database will be

问题 Im using this: SELECT * WHERE id=MAX(id) FROM history; But my query is empty. I have also tried this (This one works): SELECT MAX(id) AS max_id FROM history; But obviusly my query only contains the max_id key. What am I doing wrong with the first one? 回答1: You need to add another level of select for the MAX , like this: SELECT * WHERE id=(SELECT MAX(id) from history) FROM history; A better approach would be to order by id in descending order, and limit the output to a single row: SELECT *