如何创建3个select SQL语句的数据表

Question

我有一个包含一个表的数据库，我有3个选择SQL语句。

这些选择项目具有不同的条件。如何合并这个3 SQL命令的答案？

我不想将它们逐行合并到数据表中。还有其他办法吗？

有点像这样......

           OleDbCommand cmd = new OleDbCommand("select top "+ cont0 +" * from (select * from db where tablenumber=0)  order by ID ASC", mycon);
        OleDbDataAdapter adapt=new OleDbDataAdapter(cmd);
        DataTable dt = new DataTable();
        DataTable dttemp = new DataTable();
        adapt = new OleDbDataAdapter(cmd);
        adapt.Fill(dt);
        cmd = new OleDbCommand("select top "+ cont1 +" * from (select * from db where tablenumber=1)  order by ID ASC", mycon);
        adapt = new OleDbDataAdapter(cmd);
        adapt.Fill(dttemp);
        foreach (DataRow row in dttemp.Rows)
        {
            dt.Rows.Add(row.ItemArray);
        }
        if (cont2 != 0)
        {
            cmd = new OleDbCommand("select top " + cont2 + " * from (select * from db where tablenumber=2)  order by ID ASC", mycon);
            adapt = new OleDbDataAdapter(cmd);
            dttemp = new DataTable();
            adapt.Fill(dttemp);
            foreach (DataRow row in dttemp.Rows)
            {
                dt.Rows.Add(row.ItemArray);
            }
        }
        if (cont3 != 0)
        {
            cmd = new OleDbCommand("select top " + cont3 + " * from (select * from db where tablenumber=3)  order by ID ASC", mycon);
            adapt = new OleDbDataAdapter(cmd);
            dttemp = new DataTable();
            adapt.Fill(dttemp);
            foreach (DataRow row in dttemp.Rows)
            {
                dt.Rows.Add(row.ItemArray);
            }
        }
        if (cont4 != 0)
        {
            cmd = new OleDbCommand("select top " + cont4 + " * from (select * from db where tablenumber=4)  order by ID ASC", mycon);
            adapt = new OleDbDataAdapter(cmd);
            dttemp = new DataTable();
            adapt.Fill(dttemp);
            foreach (DataRow row in dttemp.Rows)
            {
                dt.Rows.Add(row.ItemArray);
            }
        }
        if (cont5 != 0)
        {
            cmd = new OleDbCommand("select top " + cont5 + " * from (select * from db where tablenumber=5)  order by ID ASC", mycon);
            adapt = new OleDbDataAdapter(cmd);
            dttemp = new DataTable();
            adapt.Fill(dttemp);
            foreach (DataRow row in dttemp.Rows)
            {
                dt.Rows.Add(row.ItemArray);
            }
        }

Answer 1

您可以像这样合并它们：

"select * from
    (select *, row_number() over(partition by field order by id) as rn 
     from table1 where field in(0, 5, 9)) t 
 where rn <= " + cont

修改

string command = "select * from ( select top "+ cont0 +" * from db where tablenumber=0 order by ID) t union all 
                  select * from ( select top "+ cont1 +" * from db where tablenumber=1 order by ID) t";

if (cont2 != 0)
    comand += " union all select * from ( select top " + cont2 + " * from db where tablenumber=2 order by ID) t";

if (cont3 != 0)
    comand += " union all select * from ( select top " + cont3 + " * from db where tablenumber=3 order by ID) t";

....

OleDbCommand cmd = new OleDbCommand(command, mycon);
OleDbDataAdapter adapt=new OleDbDataAdapter(cmd);
DataTable dt = new DataTable();
....