数据表/内部联接

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.

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