database

问题 In database theory, what is the difference between "conflict serializable" and "conflict equivalent"? My textbook has a section on conflict serializable but glosses over conflict equivalence. These are probably both concepts I am familiar with, but I am not familiar with the terminology, so I am looking for an explanation. 回答1: Just two terms to describe one thing in different ways. Conflict equivalent : you need to say Schedule A is conflict equivalent to Schedule B. it must involve two

问题 I want Insert DateTime Type Value.But I got this Error Source Code private void Execute(string query) { SQLiteCommand cmd = new SQLiteCommand(query, conn); int result = cmd.ExecuteNonQuery(); Debug("Executed query: {0} Result: {1}", query, result); } private string DEscape(DateTime time) { return time.ToString(@"\'yyyy-MM-dd\'"); } public void InsertVideo(string videoID, DateTime releaseDate, string[] genres) { string genreStr = ""; foreach (string g in genres) { genreStr = genreStr +

问题 I want Insert DateTime Type Value.But I got this Error Source Code private void Execute(string query) { SQLiteCommand cmd = new SQLiteCommand(query, conn); int result = cmd.ExecuteNonQuery(); Debug("Executed query: {0} Result: {1}", query, result); } private string DEscape(DateTime time) { return time.ToString(@"\'yyyy-MM-dd\'"); } public void InsertVideo(string videoID, DateTime releaseDate, string[] genres) { string genreStr = ""; foreach (string g in genres) { genreStr = genreStr +

问题 I made a python program here and i wanted to send the code to my friend and he was unable to add values through the program to my database, is there a way i can allow his access. Code: from tkinter import * import mysql.connector as mysql root = Tk() def flush(*args): name = nme.get() phone = ph.get() emirate = e_id.get() con = mysql.connect(host='127.0.0.1', user='root', password='monkey123', database='NZ') c = con.cursor() c.execute("Insert into gliy VALUES ('"+name+"','"+str(phone)+"','"

问题 Here are the compound index and single index I have for this Collection: ///db.Collection.getIndexes() /* 1 */ { "v" : 2, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "service.Collection" }, /* 2 */ { "v" : 2, "key" : { "FirstId" : 1, "SecondId" : 1, "CreationTime" : -1 }, "name" : "FirstIdSecondIdCreationTime", "collation" : { "locale" : "en", "caseLevel" : false, "caseFirst" : "off", "strength" : 1, "numericOrdering" : false, "alternate" : "non-ignorable", "maxVariable" : "punct",

问题 I'm using ON DUPLICATE KEY UPDATE to handle duplicate inserts on a table, in order that they are discarded. In my case it's a simple table storing tags: id (int, PK, AI, unsigned, not null) tag (varchar 25, not null, unique) This is working fine, but I need to retrieve the ID - either the insert ID, on successful insert, or the existing ID, if it's a duplicate. I'm getting insert ID = 0 where ON DUPLICATE KEY UPDATE fires, which I guess is expected behaviour since no insert took place. Is

问题 I'm using ON DUPLICATE KEY UPDATE to handle duplicate inserts on a table, in order that they are discarded. In my case it's a simple table storing tags: id (int, PK, AI, unsigned, not null) tag (varchar 25, not null, unique) This is working fine, but I need to retrieve the ID - either the insert ID, on successful insert, or the existing ID, if it's a duplicate. I'm getting insert ID = 0 where ON DUPLICATE KEY UPDATE fires, which I guess is expected behaviour since no insert took place. Is

问题 I am having trouble with this error when Adding new migration. The filter expression 'e => Not(e.IsDeleted)' cannot be specified for entity type 'Babysitter'. A filter may only be applied to the root entity type in a hierarchy. What I am doing is that I have 2 classes Babysitter and Parent that both need to be ApplicationUsers, because they have different properties. So I made them inherit the ApplicationUser class and extended them. This is the ApplicationUser class. public class

问题 I need to modify the UpgradeCode property of the Upgrade MSI table via C#. This code works ok with other tables' properties, but throws an error when I'm trying to modify these. using (var database = new Database(TEMPDATABASE, DatabaseOpenMode.Direct)) { string upgradeCode = Guid.NewGuid().ToString("B").ToUpper(); database.Execute("Update `Upgrade` Set `Upgrade`.`UpgradeCode` = '{0}'", upgradeCode); } The error is: Microsoft.Deployment.WindowsInstaller.InstallerException: 'Function failed

问题 I have a .CSV export file from a SQL Server database, with a phone number field (number type) that field values started with leading zero. Leading zero is presented in the CSV file. When I attempt to mongoimport it to DB (in string type) I find data imported without leading zero. The target field number is string. How can I solve this problem? 回答1: you can specifically define the type of the field using the import option --columnsHaveTypes Instructs mongoimport that the field list specified