Daniel Dashkevich's questions

无法在云上的 ibm db2 中创建查询。首先尝试使用 SYS_CONNECT_BY_PATH 但显示意外令牌“PRIOR”

SELECT ID0, MNAME, SYS_CONNECT_BY_PATH(MNAME, '/') AS path
FROM MAIN WHERE id0 IN (40,60) CONNECT BY NOCYCLE PRIOR id0=main_id;

我尝试像以前在 SQLite 中那样做，一切正常，但这里出现错误错误使用字符串列、主机变量、常量或函数“MNAME”

WITH paths (id, path) AS (SELECT id0, Mname FROM main WHERE main_id IS NULL 
UNION SELECT main.id0,  paths.path ||'/'|| main.Mname FROM main inner join paths on main.main_id = paths.id) 
SELECT a.id0, path FROM main AS a INNER JOIN paths AS b ON a.id0 = b.id where a.id0 in (40,60);

求助，怎么办？

我正在尝试从数据库中卸载数据，但 CASE 语句不起作用，它给出的是空单元格而不是数据。在 SQLiteStudio 中，所有内容都通过此请求正确卸载。怎样成为？

conn = new SQLiteConnection(conn_string);
conn.Open();
SQLiteCommand command = new SQLiteCommand();
command.Connection = conn;
string query = "select count(id) as 'Всего заказов', case when status = 1 then count(id) else null end as 'Завершенных заказов', case when status = 1 then sum(cost) else null end as 'Прибыль' from appointment";
command.CommandText = query;

SQLiteDataAdapter da = new SQLiteDataAdapter(command);
dt = new DataTable();
da.Fill(dt);
dataGridView1.DataSource=dt;
conn.Close();

您需要按日期进行过滤，表格通过以下代码填充：

    DataSet dataSet = new DataSet();
    OleDbDataAdapter dataAdapter = new OleDbDataAdapter();
    OleDbDataAdapter dataAdapter1 = new OleDbDataAdapter();

    string query = "select * from Договор";
    string query1 = "select * from Поставщики";

    conn = new OleDbConnection(conn_string);

    dataAdapter.SelectCommand = new OleDbCommand(query, conn);
    dataAdapter1.SelectCommand = new OleDbCommand(query1, conn);

    dataAdapter.TableMappings.Add("Table", "Договор");
    dataAdapter1.TableMappings.Add("Table", "Поставщики");

    dataAdapter.Fill(dataSet);
    dataAdapter1.Fill(dataSet);

    BindingSource dogSource = new BindingSource();
    dogSource.DataSource = dataSet;
    dogSource.DataMember = "Договор";
    dataGridView1.DataSource = dogSource;

    BindingSource postSource = new BindingSource();
    postSource.DataSource = dataSet;
    postSource.DataMember = "Поставщики";

    DataGridViewComboBoxColumn comboColumn = new DataGridViewComboBoxColumn();
    comboColumn.HeaderText = "Поставщики";
    comboColumn.DataSource = postSource;

    comboColumn.DataPropertyName = "Код поставщика";

    comboColumn.DisplayMember = "Название";

    comboColumn.ValueMember = "Код поставщика";

以前，我在任何地方都使用过过滤，

    DataView dv = new DataView(dt);
    dv.RowFilter = string.Format(" CONVERT([Дата заключения], 'System.DateTime') >= '{0:dd.MM.yyyy}' AND CONVERT([Дата заключения], 'System.DateTime') <= '{0:dd.MM.yyyy}'",
    dateTimePicker1.Value.ToShortDateString());;
    dataGridView1.DataSource=dv;

但现在这不起作用，很可能是因为 DataSource。不幸的是，我不是这方面的专家，我将不胜感激。

有一个填写表格的代码。但是我不知道如何在“供应商”列中的组合框中的值发生变化时强制“供应商代码”列中的值发生变化。我将不胜感激提示和帮助。

conn = new OleDbConnection(conn_string);
conn.Open();
OleDbCommand command = new OleDbCommand();
command.Connection = conn;
string query = "select Договор.*, Поставщики.Название from Договор, Поставщики where Договор.[Код поставщика] = Поставщики.[Код поставщика] order by [№ договора]";
command.CommandText = query;

OleDbDataAdapter da = new OleDbDataAdapter(command);
dt = new DataTable();
da.Fill(dt);
Поставщики.DisplayMember = "Название";
Поставщики.ValueMember = "Код поставщика";
Поставщики.DataSource = dt;
dataGridView1.DataSource=dt;
this.dataGridView1.Columns["Название"].ReadOnly = true;
conn.Close();

当从组合框中选择索引时，有一个代码可以在 datagridview 中显示行。但是在重置时，它comboBox1.SelectedItem = null给出了一个错误。为什么它给出是可以理解的，但如何解决它却不是。

for (int i = 0; i < dataGridView1.Rows.Count - 1; i++)
{       
    dataGridView1.CurrentCell = null;
    dataGridView1.Rows[i].Visible = false;
    for (int c = 0; c < dataGridView1.Columns.Count; c++)
    {
         if(dataGridView1[c, i+1].RowIndex.ToString() == comboBox1.SelectedItem.ToString())
         {
            dataGridView1.Rows[i].Visible = true;
            break;
         }
    }
}