C# 中的简单 SQL 选择？
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Simple SQL select in C#?
提问by Chris
On my current project, to get a single value (select column from table where id=val), the previous programmer goes through using a datarow, datatable and an sqldatadapter (and of course sqlconnection) just to get that one value.
在我当前的项目中，为了获得单个值（从表中选择 id=val 的列），以前的程序员使用数据行、数据表和 sqldatadapter（当然还有 sqlconnection）只是为了获得那个值。
Is there an easier way to make a simple select query? In php, I can just use mysql_queryand then mysql_resultand I'm done.
有没有更简单的方法来进行简单的选择查询？在 php 中，我可以只使用mysql_query然后mysql_result我就完成了。
It would be nice if I could just do:
如果我可以这样做就好了：
SqlConnection conSql = new SqlConnection(ConnStr);
SomeSqlClass obj = new SomeSqlClass(sql_string, conSql);
conSql.Close();
return obj[0];
Thanks for any tips.
感谢您提供任何提示。
采纳答案by womp
You can skip the DataReaderand the DataAdapterand just call ExecuteScalar()on the sql command.
您可以跳过DataReader和DataAdapter并直接调用ExecuteScalar()sql 命令。
using (SqlConnection conn = new SqlConnection(connString))
{
SqlCommand cmd = new SqlCommand("SELECT * FROM whatever
WHERE id = 5", conn);
try
{
conn.Open();
newID = (int)cmd.ExecuteScalar();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
回答by womp
Actually, there is a method SqlCommand.ExecuteScalar() that will simply return the first field from the first row of the returned results. Just for you.
实际上，有一个方法 SqlCommand.ExecuteScalar() 将简单地从返回结果的第一行返回第一个字段。只为你。
.NET Framework Class Library SqlCommand..::.ExecuteScalar Method
.NET Framework 类库 SqlCommand..::.ExecuteScalar 方法
Executes the query, and returns the first column of the first row in the result set returned by the query. Additional columns or rows are ignored.
执行查询，返回查询返回的结果集中第一行的第一列。其他列或行将被忽略。
回答by Fahad
you can use SqlCommands executeScalar function. Please look at the following link
您可以使用 SqlCommands 的 executeScalar 函数。请看下面的链接
http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.executescalar.aspx
http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.executescalar.aspx
回答by LukeH
You can do something very similar:
你可以做一些非常相似的事情：
using (SqlConnection conn = new SqlConnection(ConnStr))
using (SqlCommand cmd = new SqlCommand(sql_string, conn))
{
conn.Open();
return cmd.ExecuteScalar();
}
回答by Kristoffer Deinoff
You are probably looking for SqlCommandand SqlDataReader
您可能正在寻找SqlCommand和SqlDataReader
Dictionary<int, string> users = new Dictionary<int, string>();
using(SqlConnection connection = new SqlConnection("Your connection string"))
{
string query = "SELECT UserId, UserName FROM Users";
SqlCommand command = new SqlCommand(query, connection);
connection.Open();
using (SqlDataReader reader = command.ExecuteReader())
{
while (reader.Read())
users.Add(reader.GetInt32(0), reader.GetString(1));
}
connection.Close();
}
