Your string is going to look something like this:
String query = "SELECT Value, IdCategory, CreateDate, Description, IdUser FROM"
+ " profit WHERE IdUser = '" + USER + "'";
Make sure you add the single quotes around your user variable like I did.
Then you will want to do something like:
using(MySqlCommand cmd = new MySqlCommand(query, conn))
{
cmd.CommandText = query;
MySqlDataReader reader = cmd.ExecuteReader();
while(reader.Read())
{
}
reader.Close();
conn.Close();
}
This is assuming you're using MySql Connect/NET, since you haven't specified. I have basically just provided a simplified version of the article in the link I gave in the comments. It's a good pretty good example - between what I've given you and that article you should be able to get this done.
Here's the link again:
Connect C# to MySQL[
^]