sqlite

问题 I wanna add imagefield to my models.py and upload in my media_cdn directory but when i migrate to base my model.py he give this error django.db.utils.IntegrityError: NOT NULL constraint failed: products_product.image ERROR WITH IMAGE FIELD Output from cmd operation.database_forwards(self.app_label, schema_editor, old_state, project_state) File "C:\Users\PANDEMIC\Desktop\td10\lib\site-packages\django\db\migrations\operations\fields.py", line 84, in database_forwards field, File "C:\Users

问题 Is there an elegant way of getting a single result from an SQLite SELECT query when using python 2.7? for example: conn = sqlite3.connect('db_path.db') cursor=conn.cursor() cursor.execute("SELECT MAX(value) FROM table") for row in cursor: for elem in row: maxVal = elem is there a way to avoid those nested for s and get the value directly? I've tried maxVal = cursor[0][0] without any success. 回答1: I think you're looking for Cursor.fetchone() : cursor.fetchone()[0] 回答2: Or you could write a

问题 Is there an elegant way of getting a single result from an SQLite SELECT query when using python 2.7? for example: conn = sqlite3.connect('db_path.db') cursor=conn.cursor() cursor.execute("SELECT MAX(value) FROM table") for row in cursor: for elem in row: maxVal = elem is there a way to avoid those nested for s and get the value directly? I've tried maxVal = cursor[0][0] without any success. 回答1: I think you're looking for Cursor.fetchone() : cursor.fetchone()[0] 回答2: Or you could write a

问题 In my app I've got to implement some UI and Sync service. It runs in the background and updates data. Sync service is not very simple, it uses multithreading. So, here is my story: When I started developing this app I didn't know anything about sqlite, so I just didn't use any thread synchronization in Java. Result: I got many Exceptions like "SQLiteException: database is locked: BEGIN EXCLUSIVE;" Then I synchronized all my transactions with regular Java synchronized () {} block. Everything

问题 I know SQLite Data Base is used in mobile devices (Android, iPhone) and it is light, takes only Kb space. Is there any limitation in SQLite? I want to know how they are different. 回答1: Every SQL database uses its own implementation of the language that varies slightly. While basic queries are almost universal, there are notable nuances between MySQL, PostgreSQL, Microsoft SQL Server, Oracle Database, etc. What's particularly notable about SQLite is that unlike all the others mentioned above,

问题 I know SQLite Data Base is used in mobile devices (Android, iPhone) and it is light, takes only Kb space. Is there any limitation in SQLite? I want to know how they are different. 回答1: Every SQL database uses its own implementation of the language that varies slightly. While basic queries are almost universal, there are notable nuances between MySQL, PostgreSQL, Microsoft SQL Server, Oracle Database, etc. What's particularly notable about SQLite is that unlike all the others mentioned above,

问题 I know SQLite Data Base is used in mobile devices (Android, iPhone) and it is light, takes only Kb space. Is there any limitation in SQLite? I want to know how they are different. 回答1: Every SQL database uses its own implementation of the language that varies slightly. While basic queries are almost universal, there are notable nuances between MySQL, PostgreSQL, Microsoft SQL Server, Oracle Database, etc. What's particularly notable about SQLite is that unlike all the others mentioned above,

问题 I am using c# sqlite version 3. My application requires saving up to 20 columns of data at 4000Hz. To accomplish this I am using threads that take commands from a queue and periodically write/read to the database. Currently, I am just working on the writing portion and have found that ExecuteNonQueryAsync() and ExecuteNonQuery() have relatively the same execution time which makes no sense to me. My function is as follows: public async Task<int> dumpStorage(string cmdStr) { int r; using

问题 I'm trying to create a large SQLite database from around 500 smaller databases (each 50-200MB) to put into Django, and would like to speed up this process. I'm doing this via a custom command. This answer helped me a lot, in reducing the speed to around a minute each in processing a smaller database. However it's still quite a long time. The one thing I haven't done in that answer is to disable database indexing in Django and re-create them. I think this matters for me as my database has few

问题 Environment : VS2019 , .NET 4.8 , EF 6 , SQLite , WPF App (.NET Framework) I am following this Microsoft official tutorial to create a code-first app, called WPF_EF6 using SQLite. With the configuration shown below, I am getting an error about failing to connect to SQL Server. But as you can see in the App.config file below, there is no SQL Server is involved here? Question : what may I be missing here? And how can we resolve the issue? App compiles fine but throws this runtime error. I