选择表时，Sql删除重复

Question

我的sql中有一个表，例如名称和城市。

我想创建一个Select Command来获取所有城市，并从结果中删除重复项。

我正在使用的选择：

        string citiesSelect = "SELECT [city] FROM [people] ORDER BY [city]";
        CitiesDataSource.SelectCommand = citiesSelect;
        CitiesDataSource.Select(DataSourceSelectArguments.Empty);
        DropDownList2.DataSourceID = CitiesDataSource.ID;

Answer 1

使用DISTINCT。

 string citiesSelect = "SELECT DISTINCT [city] FROM [people] ORDER BY [city]";
        CitiesDataSource.SelectCommand = citiesSelect;
        CitiesDataSource.Select(DataSourceSelectArguments.Empty);
        DropDownList2.DataSourceID = CitiesDataSource.ID;

Answer 2

考虑以下一行：

string citiesSelect = "SELECT DISTINCT [city] FROM [people] ORDER BY [city]";

Answer 3

尝试此查询：

SELECT DISTINCT [city] FROM [people] ORDER BY [city]

可以找到DISTINCT的文档here。