数据表/内部联接 [英] Data Table / Inner Join

问题描述

protected decimal chk_trainee(string m_memcode, string m_date, int session, SqlConnection conn)
    {
        SqlCommand cmd = new SqlCommand("SELECT * FROM [t_memsch] WHERE [m_schdate]='" + m_date + "' AND [m_schsession]='" + session + "' AND [m_memcode]='" + m_memcode + "'", conn);
        SqlDataAdapter sda = new SqlDataAdapter(cmd);
        DataTable ds = new DataTable();
        sda.Fill(ds);

        string m_jobtype = ds.Rows[0]["m_jobtype"].ToString();
        string m_memlevel = ds.Rows[0]["m_memlevel"].ToString();

        sda.Dispose();

        SqlCommand cmd1 = new SqlCommand("SELECT * FROM [m_jobtype] WHERE [m_cjobtypedesc]='" + m_jobtype + "'", conn);
        SqlDataAdapter sda1 = new SqlDataAdapter(cmd1);
        DataTable ds1 = new DataTable();
        sda.Fill(ds1);

        string m_jobtypecode = ds1.Rows[0]["m_jobtypecode"].ToString();

        sda.Dispose();
        
        SqlCommand cmd2 = new SqlCommand("SELECT * FROM [m_allowance] WHERE [m_jobtypecode]='" + m_jobtypecode + "' AND [m_memlevel]='" + m_memlevel + "' AND '" + m_date + "' BETWEEN [m_effdate] AND [m_expiredate]", conn);
        SqlDataAdapter sda2 = new SqlDataAdapter(cmd2);
        DataTable ds2 = new DataTable();
        sda.Fill(ds2);

        return Convert.ToDecimal(ds2.Rows[0]["m_amt"].ToString());;
   
    }

这些编码有问题，我想是由于我不能在一个函数中拥有3个数据表.我知道使用内部联接很容易解决，但是我不知道如何使用内部联接.请任何人帮忙吗?

These coding have problems, i guess is due to i cant have 3 datatables in one function. I know it is easy to solve by using inner join, but however, i dunno how to use innerjoin. Please anyone help? thanks.

推荐答案

您可以根据需要拥有任意数量的DataTable.

但是，这样做真正有用的是让您清楚明确地说明您遇到的问题. 这些编码有问题"完全是垃圾.

You can have as many DataTables as you need.

What would be really useful with this though is for you to clearly and articulately explain what problem you are having. "These coding have problems" is complete rubbish.

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