Question

怎么判断数据库中是否存在相同的数据

Answer 1

SqlConnection con = new SqlConnection("Data Source=10.168.1.5;Initial Catalog=data;User ID=sa;password=sa;Integrated Security=False");
con.Open();
SqlCommand cmd = new SqlCommand(string.Format("select Count(*) from newtable where a= '{0}'", s1), con);
if ((int)cmd.ExecuteScalar() > 0)
{
listBox1.Items.Add(s1 + " 数据已经存在");
}
else
{
string sql = "insert into newtable(a,b,c) values('" + s1 + "','" + s2 + "','" + s3 +"')";
cmd.CommandText = sql;
cmd.ExecuteNonQuery();
listBox1.Items.Add(s1 + " 成功添加");
}
cmd.Dispose();
con.Close();