将多个值发送到 Mysql 查询

Question

这是故事：

我有一个检查列表，其中包含我数据库中的项目需要编写查询以仅获取 selected 项目详细信息，然后填充 gridviwe

 object[] items = checkedListBox1.CheckedItems.OfType<object>().ToArray();

        foreach (var item in items)
        {



            string connectionString = "server=127.0.0.1;uid=root;pwd=admin;database=per_update;";
            string query = "select * from tblcenters where centerName in('" + item + "')";
            using (MySqlConnection conn = new MySqlConnection(connectionString))
            {
                using (MySqlDataAdapter adapter = new MySqlDataAdapter(query, conn))
                {
                    DataTable ds = new DataTable();
                    adapter.Fill(ds);


                    dataGridView1.DataSource = ds;
                }

} }

我写了这段代码，它只得到了我 select 最后一项的详细信息。但我需要所有项目的详细信息 select

请不要担心在查询中不使用参数，因为这是一个示例

Answer 1

已更新。也许您应该使用 StringBuilder 来完成这项任务。如果您对每个选定的项目都提出请求，效率也会非常低下。像下面这样的东西可能是更好的解决方案：

StringBuilder sb = new StringBuilder();
sb.Append("select * from tblcenters where centerName in(");
for(int i=0;i<length;i++)
{
  sb.Append('" + item[i] + "' + ",");
}
sb.Length--; // to get rid of the last comma (',')
sb.Append(")");
string query = sb.ToString();

Answer 2

object[] items = checkedListBox1.CheckedItems.OfType<object>().ToArray();
string InStatement="("; //prepare the in clause
foreach (var item in items)
{
   InStatement+=item+",";

}
InStatement=InStatement.Substring(0, InStatement.Length - 1)+")";///trim last comma and add ending parenthesis
string connectionString = "server=127.0.0.1;uid=root;pwd=admin;database=per_update;";
string query = "select * from tblcenters where centerName in"+InStatement;
using (MySqlConnection conn = new MySqlConnection(connectionString))
{
    using (MySqlDataAdapter adapter = new MySqlDataAdapter(query, conn))
    {
      DataTable ds = new DataTable();
      adapter.Fill(ds);
      dataGridView1.DataSource = ds;
    }
}

Answer 3

尝试构建必须在 WHERE IN 语句中使用的字符串，如下所示：

var whereValues = "";

foreach (var item in items) {
    whereValues += ", '" + item + "'";
}

whereValues += whereValues.Substring(2, whereValues.Length-2);

string query = "select * from tblcenters where centerName in(" + whereValues + ")";

Answer 4

您的问题是由循环内的项目值重置引起的。
你说不需要使用参数，但是在这种情况下使用它们并没有太复杂并且有更安全的代码

// Get all the checked items in a list of strings...
List<string> values = checkedListBox1.CheckedItems.Cast<string>().ToList();

List<MySqlParameter> prms = new List<MySqlParameter>();
List<string> prmsNames = new List<string>();

// Loop over the values and build the parameter names and the parameters
for (int x = 0; x < values.Count; x++)
{
    // The parameter with a conventional name
    prms.Add(new MySqlParameter("@" + x.ToString(), MySqlDbType.VarChar) { Value = values[x] });
    // the parameter' names
    prmsNames.Add("@" + x.ToString());
}

// The command text
string query = @"select * from tblcenters 
                 where centerName in (" + 
                string.Join(",", prmsNames) + ")";

using (MySqlConnection conn = new MySqlConnection(connectionString))
using (MySqlDataAdapter adapter = new MySqlDataAdapter(query, conn))
{
    // Add the parameters collection to the select command....
    adapter.SelectCommand.Parameters.AddRange(prms.ToArray());
    DataTable ds = new DataTable();
    adapter.Fill(ds);
    dataGridView1.DataSource = ds;
}

将多个值发送到 Mysql 查询

Send Multiple Values to Mysql Query

c#

mysql

sql

checklistbox