sqlite

问题 I have a small application for android written in java, I am rewriting using flutter. Is it possible to transition to the new version by keeping the SQLite database structure intact, including all data? I ran a test, and although I was able to overwrite the application, the data was lost after upgrade. 回答1: If anyone needed it, I was able to read the data from the existing database and write to it using flutter. My previous test had gone wrong because the bases were allocated in separate

问题 I have a small application for android written in java, I am rewriting using flutter. Is it possible to transition to the new version by keeping the SQLite database structure intact, including all data? I ran a test, and although I was able to overwrite the application, the data was lost after upgrade. 回答1: If anyone needed it, I was able to read the data from the existing database and write to it using flutter. My previous test had gone wrong because the bases were allocated in separate

问题 In my application, there exist more than one process, and in each process, I need access the same SQLite database (of course, it means more than 2 theads), so I worried about not only the thread-safety about the SQLite, but also the process-safety. One solution for this case is using content-provider. But from android sdk, it warns that its methods may be called from multiple threads and therefore must be thread-safe. If content provider itself not necessarily means thread-safe, how can I

问题 In my application, there exist more than one process, and in each process, I need access the same SQLite database (of course, it means more than 2 theads), so I worried about not only the thread-safety about the SQLite, but also the process-safety. One solution for this case is using content-provider. But from android sdk, it warns that its methods may be called from multiple threads and therefore must be thread-safe. If content provider itself not necessarily means thread-safe, how can I

问题 I am unable to import the sqlite3 module in Python, version 3.5.0. Here's what I get: >>> import sqlite3 Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/local/lib/python3.5/sqlite3/__init__.py", line 23, in <module> from sqlite3.dbapi2 import * File "/usr/local/lib/python3.5/sqlite3/dbapi2.py", line 27, in <module> from _sqlite3 import * ImportError: No module named '_sqlite3' I know, I know, there are PLENTY of StackOverflow posts and support forums across

问题 I am unable to import the sqlite3 module in Python, version 3.5.0. Here's what I get: >>> import sqlite3 Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/local/lib/python3.5/sqlite3/__init__.py", line 23, in <module> from sqlite3.dbapi2 import * File "/usr/local/lib/python3.5/sqlite3/dbapi2.py", line 27, in <module> from _sqlite3 import * ImportError: No module named '_sqlite3' I know, I know, there are PLENTY of StackOverflow posts and support forums across

问题 I'm trying execute this query in SQLite: SELECT * FROM customers WHERE rating = ANY (SELECT rating FROM customers WHERE city = 'Rome'); But received this error: Query Error: near "SELECT": syntax error Unable to execute statement If I replace rating = ANY to rating IN , everything works fine. Can someone show me how ANY statement works in SQLite and what I am doing wrong? 回答1: AFAIK, SQLite doesn't have an ANY operator. You could, however, use the IN operator to get the required functionality

问题 I'm trying execute this query in SQLite: SELECT * FROM customers WHERE rating = ANY (SELECT rating FROM customers WHERE city = 'Rome'); But received this error: Query Error: near "SELECT": syntax error Unable to execute statement If I replace rating = ANY to rating IN , everything works fine. Can someone show me how ANY statement works in SQLite and what I am doing wrong? 回答1: AFAIK, SQLite doesn't have an ANY operator. You could, however, use the IN operator to get the required functionality

问题 I have a test fixture in which I initialize my SQLite in-memory dbcontext, shown below: public static MYAPPDBContext Create() { var options = new DbContextOptionsBuilder<MYAPPDBContext>() .UseSqlite("DataSource=:memory:") .Options; var context = new MYAPPDBContext(options); context.Database.OpenConnection(); // this is where exception is thrown context.Database.EnsureCreated(); return context; } When I call the Create() method, I get the following NullReferenceException: System

问题 I have been looking at similar questions on Stack but any of them seems to be helpful to me. I have the following table called "Likes": ID1 ID2 1689 1709 1709 1689 1782 1709 1911 1247 1247 1468 1641 1468 1316 1304 1501 1934 1934 1501 1025 1101 I want to get the unique pairs between the two columns ID1 and ID2. That is: ID1 ID2 1689 1709 1501 1934 Any idea? Thx. 回答1: It looks like you want pairs that exist in both versions, i.e. both as (x, y) and (y, x). Can be done with a EXISTS query: