如何防止SQL数据库中的类似(重复)条目

//CHECK IF COMPLETE DUPLICATE
query = "SELECT * FROM TBL_FLAVORS WHERE flavor_name = @flavor_name AND flavor_supplierid = @supplier_id";
                    using (SqlConnection con = new SqlConnection(connstring))
{
     con.Open();
     using (SqlCommand cmd = new SqlCommand(query, con))
     {
          SqlDataReader read;
          cmd.Parameters.AddWithValue("@flavor_name", txtFlavorName.Text.ToString());
          cmd.Parameters.AddWithValue("@supplier_id", supplierid);
          read = cmd.ExecuteReader();
          if (read.Read())
          {
                MessageBox.Show("This flavor for this supplier already exists.");
                return;
          }
          read.Close();
      }
} 
//CHECK IF ALMOST SIMILAR
//IF RECORD FOUND, RETURN
//OTHERWISE, PROCEED TO UPDATE/INSERT
query = "SELECT * FROM TBL_FLAVORS WHERE (flavor_name LIKE @flavor_name OR flavor_name LIKE @flavor_name2 OR FLAVOR_NAME LIKE @flavor_name3) AND flavor_supplierid = @supplier_id";
using (SqlConnection con = new SqlConnection(connstring))
{
     con.Open();
     using (SqlCommand cmd = new SqlCommand(query, con))
     {
           string flavorname = "%" + txtFlavorName.Text.ToString()+ "%";
           string flavorname2 = "" + txtFlavorName.Text.ToString() + "%";
           string flavorname3 = "%" + txtFlavorName.Text.ToString() + "";
           SqlDataReader read;
           cmd.Parameters.AddWithValue("@flavor_name", flavorname);
           cmd.Parameters.AddWithValue("@flavor_name2", flavorname2);
           cmd.Parameters.AddWithValue("@flavor_name3", flavorname3);
           cmd.Parameters.AddWithValue("@supplier_id", supplierid);
           read = cmd.ExecuteReader();
           if (read.Read())
           {
                 DialogResult dialog = MessageBox.Show("It is possible that this flavor for this supplier already exists. Do you want to continue?", "", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
                 if (dialog == DialogResult.No)
                 {
                       return;
                 }
            }
            read.Close();
      }
}

小组成员问，如果已经有一个"英寸"，用户输入了一个"英寸"怎么办?它应该被认为是复制品。或者假设数据库中有一个'chocolate'，如果用户输入'chocolate'，它应该要求确认。