C# 使用来自多个Sql表的唯一数据值字段绑定下拉列表？

我想从多个SqlDatabase表中选择多个列，以便使用唯一的数据值字段绑定DropDownList

下面是我的C代码和SqlQuery，用于从表1中选择多个列：

// Create a dropdownlist inside the dynamically created panel and insert in the 1st row 1st cell of dynamic html table
var DDL = new WebForms.DropDownList();
DDL.ID = "MainDDL";
SqlDataSource da = new SqlDataSource();
da.ConnectionString = connection;
string item = "--Select--";
da.SelectCommand = "SELECT DATA_TYPE + '_' + convert(varchar(10), ROW_NUMBER() OVER(ORDER BY DATA_TYPE))as DATA_TYPE, COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE (TABLE_NAME = 'MyTable1' AND COLUMN_NAME IN ('Column1','Column2','Column3','Column4','Column5'))";
DDL.DataSource = da;
DDL.DataTextField = "COLUMN_NAME";
DDL.DataValueField = "DATA_TYPE";
DDL.DataBind();  

所需解决方案： 要从多个Sql表中选择的多列：

如何在下面的Sql查询中从Mytable2中选择column1

选择数据类型+'''''''+convertvarchar10，按数据类型排列的行数作为数据类型，从信息模式中选择列名称。列中，表名称='MyTable1'和列名称位于'Column1'、'Column2'、'Column3'、'Column4'、'Column5'

问：如何在下面的Sql查询中包括Mytable2及其column1

A:

SELECT 
    DATA_TYPE + '_' + convert(varchar(10), ROW_NUMBER() OVER(ORDER BY DATA_TYPE))as DATA_TYPE, 
    COLUMN_NAME 
FROM INFORMATION_SCHEMA.COLUMNS 
WHERE 
    (TABLE_NAME = 'MyTable1' AND COLUMN_NAME IN ('Column1','Column2','Column3','Column4','Column5'))
    OR
    (TABLE_NAME = 'MyTable2' AND COLUMN_NAME IN ('Column1'))