是否可以检查SQLite表是否存在.

Question

我有以下代码:

        dbcon = DependencyService.Get<ISQLite>().GetConnection();

        // create the tables
        dbcon.CreateTable<Category>();
        dbcon.CreateTable<Settings>();

        var settings = dbcon.Table<Settings>().ToList();
        if (settings.Count <= 0)
        {
            var noa = new Settings { Setting = "NumberOfAnswers", Value = 5 };
            var cfs = new Settings { Setting = "CardFrontSide", Value = 0 };
            dbcon.Insert(noa);
            dbcon.Insert(cfs);
        }

        var categories = dbcon.Table<Category>().ToList();
        if (categories.Count <= 0)
        {
            InsertCategory();
        }

从我所看到的应用程序是使用SQLite-net

我想知道的是,如果有一种方法可以检查表是否存在而不是这样做,无论如何都要尝试创建它,然后尝试检查它是否有行.

Answer 1

此查询将返回数据库中的表列表

SELECT * FROM sqlite_master WHERE type = 'table';

您可以将其过滤到单行以进行"存在"检查.

SELECT * FROM sqlite_master WHERE type = 'table' AND tbl_name = 'xyz';

Answer 2

你可以这样做:

public static bool TableExists<T> (SQLiteConnection connection)
{    
    const string cmdText = "SELECT name FROM sqlite_master WHERE type='table' AND name=?";
    var cmd = connection.CreateCommand (cmdText, typeof(T).Name);
    return cmd.ExecuteScalar<string> () != null;
}

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