以下函数用于我的应用程序的较新版本，它需要向现有数据库添加一列。
public void AddColumnIfNotexist()
{
try
{
using (SQLiteCommand cmd = _DBConnection.CreateCommand())
{
cmd.CommandText = string.Format("SELECT sql FROM sqlite_master WHERE type = 'table' AND name = 'myTable'");
bool hascol = false;
using (SQLiteDataReader reader = cmd.ExecuteReader())
{
if (reader.Read())
{
//does column exists?
hascol = reader.GetString(0).Contains(String.Format("\"{0}\"", "myNewColumn"));
reader.Close();
}
}
if (!hascol)
{
StringBuilder sql = new StringBuilder(SQLMAXLENGTH);
sql.Append("ALTER TABLE Groups ADD COLUMN IsStayingRatio BIT NOT NULL DEFAULT 0");
cmd.CommandText = sql.ToString();
cmd.ExecuteNonQuery();
}
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message + "\r\n\r\n" + ex.StackTrace);
LogApp.Write("Exception ex:" + ex.Message +"stacktrace "+ex.StackTrace, LogApp.Level.Error);
}
}
}
当我执行此操作时会出现异常
database is locked
堆栈跟踪
at System.Data.SQLite.SQLite3.Step(SQLiteStatement stmt)
at System.Data.SQLite.SQLiteDataReader.NextResult()
at System.Data.SQLite.SQLiteDataReader..ctor(SQLiteCommand cmd, CommandBehavior behave)
at System.Data.SQLite.SQLiteCommand.ExecuteReader(CommandBehavior behavior)
at System.Data.SQLite.SQLiteCommand.ExecuteNonQuery(CommandBehavior behavior)
at System.Data.SQLite.SQLiteCommand.ExecuteNonQuery()
at DataPlus.DB.AddColumnIfNotexist() in D:\Projects\DB.cs:line 343
但这并不总是发生。如果 DB Fil 的大小很大，就会发生这种情况。此外，从 IDE 调试时不存在该问题。
Alter Table 查询有任何限制吗？ 谁能找出导致数据库锁定的问题吗？
最佳答案
我建议启动一个新的SQLiteCommand
Note that an SQLITE_LOCKED error is distinct from SQLITE_BUSY (5). SQLITE_BUSY means that another database connection (probably in another process) is using the database in a way that prevents you from using it. SQLITE_LOCKED means the source of contention is internal and comes from the same database connection that received the SQLITE_LOCKED error.
Sometimes people think they have finished with a SELECT statement because sqlite3_step() has returned SQLITE_DONE. But the SELECT is not really complete until sqlite3_reset() or sqlite3_finalize() have been called
关于c# - SQLite 数据库在执行 alter table 查询 C# 时被锁定，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/47027797/