sqlite

问题 I am writing code using LINQ to SQLite on UWP. To my understanding, models are templates of rows of the tables in the database. The documentations about SQLite barely mention the restrictions of the models, or how the models are converted into rows of tables. The sample codes usually provide only simple cases with primary types. My questions are： Is there any difference between a database model class and a normal class. I find at least in this example(which is a nice one, by the way), The

问题 How do I increment a column value based on previous column value in Sqlite? I need to do this for 1000+ rows. I have data in the first row say 100. I need to increment the next 1000 rows by 2. Row# ColName 1 100 2 102 3 104 4 106 I tried something like this: Update Table SET ColName = (Select max(ColName ) from Table ) + 2 but this puts 102 in all columns. 回答1: Assuming that this table has a rowid column, it is possible to count how many previous rows there are: UPDATE MyTable SET ColName =

问题 I was trying to get the exclusive lock for the SQLite database. I used sqlite3_db_mutex(db); and sqlite3_mutex_try(mutexObj) function to acquire lock, but when I tried to execute query from other shell to the same database, I was able insert row in the table,read the data from table I want is to get the LOCK to the database, so that during that time, no-one can make any change to the database, while I've acquired the lock. It is possible in Sqlite ???? 回答1: sqlite3_db_mutex locks that

问题 I'm trying to remove a row in SQLite3, on windows it removes the row, but on Ubuntu it won't. I'm not sure what's causing it/how to fix it. Both systems are running Python 3.6.5, and I did not install SQLite3 with pip. I'm running the following script, which creates a db.sqlite, creates a user table with (key, name) and inserts one user. Then it should remove it: import sqlite3 class DBHelper: def __init__(self, dbname="db.sqlite"): self.dbname = dbname self.conn = sqlite3.connect(dbname)

问题 I have following two tables in Db, with one to many relationship: self.c.execute("CREATE TABLE IF NOT EXISTS dispatch(" "id_dispatch INTEGER PRIMARY KEY AUTOINCREMENT," "d_date TEXT," "d_mill TEXT," "d_buyer TEXT," "d_addFreight INTEGER," "d_subFreight INTEGER," "d_amount INTEGER," "d_cd INTEGER," "d_comm INTEGER," "d_netAmount INTEGER)") self.c.execute("CREATE TABLE IF NOT EXISTS dispatch_products(" "dispatch_id INTEGER NOT NULL REFERENCES DISPATCH(id_dispatch)," "product INTEGER," "quantity

问题 I have following two tables in Db, with one to many relationship: self.c.execute("CREATE TABLE IF NOT EXISTS dispatch(" "id_dispatch INTEGER PRIMARY KEY AUTOINCREMENT," "d_date TEXT," "d_mill TEXT," "d_buyer TEXT," "d_addFreight INTEGER," "d_subFreight INTEGER," "d_amount INTEGER," "d_cd INTEGER," "d_comm INTEGER," "d_netAmount INTEGER)") self.c.execute("CREATE TABLE IF NOT EXISTS dispatch_products(" "dispatch_id INTEGER NOT NULL REFERENCES DISPATCH(id_dispatch)," "product INTEGER," "quantity

问题 I'm making a bot for Discord, and one of the features in this bot is a level system. I've decided to go from using JSON to store the data, to sqlite. I'm using sqlite3 in node.js and am trying to create a function to create / retrieve a player's data. My goal is to make this function return the data from the query, but I'm running my head into a brick wall trying to figure out what I'm doing wrong. I've read that I need to use callbacks sent to the query function, but that has not worked for

问题 I have 2 .txt files, and I converted them into .csv files using https://convertio.co/csv-xlsx/. Now, I would like to import these two .csv files into two databases using SQLite in Python (UI is Jupyter Notebook). These two .csv files are labeled person.csv and person_votes.csv . So, I did it by following the code given here (Importing a CSV file into a sqlite3 database table using Python): import sqlite3, csv con = sqlite3.connect(":memory:") cur = con.cursor() cur.execute("CREATE TABLE

问题 Is there a way to define a column type in SQLite that holds any datatype that SQLite supports? I have unsigned chars, signedchars, unsigned ints, signed ints, UTF-8 chars and blobs that I want to populate in a single column. Reference to any literature is also appreciated. 回答1: Just don't put a type in the column declaration, so it has NONE affinity create table my_table(my_col); SQLite has a unique dynamic typing system. It has per-value typing, but if you specify a column type, SQLite will

问题 Is there a way to define a column type in SQLite that holds any datatype that SQLite supports? I have unsigned chars, signedchars, unsigned ints, signed ints, UTF-8 chars and blobs that I want to populate in a single column. Reference to any literature is also appreciated. 回答1: Just don't put a type in the column declaration, so it has NONE affinity create table my_table(my_col); SQLite has a unique dynamic typing system. It has per-value typing, but if you specify a column type, SQLite will