A way to see query after parameters are applied?

Question

In a C# application, I'm building a query by creating a query string with parameters, then to the command adding the parameters and their values. For example:

string query = "UPDATE USERS u SET u.username = @PARM_USERNAME " +
               "WHERE u.id = @PARM_USERID ";

command.Parameters.AddWithValue("@PARM_USERNAME", user.username);
command.Parameters.AddWithValue("@PARM_USERID", user.id);

command.Connection.Open();
int res = command.ExecuteNonQuery();

It would be beneficial to see the query with parameters applied, is this doable in C#/Visual Studio? I can check the command.CommandText, but it's only showing me the same content as the query above, with the parameter placeholders there. If it helps, this is against MySQL.

score 15 · Answer 1 · answered Apr 14 '14 at 05:34

15

If you want to see the query with parameters applied:

string tmp = command.CommandText.ToString();
foreach (SqlParameter p in cmd.Parameters) {
    tmp = tmp.Replace('@' + p.ParameterName.ToString(),"'" + p.Value.ToString() + "'");
}

tmp will then hold the query with the parameters applied. Each parameter will be surrounded by single quotes.

Of course, it is NOT safe to execute. I use it for debugging purposes.

answered Apr 14 '14 at 05:34

Christopher Thomas Nicodemus

407
4
9

1

For MS SQL the 'SqlParameter' class inheritance hierarchy is System.Data.SqlClient.SqlParameter. For MySQL it would be MySql.Data.MySqlClient.MySqlParameter – PeterCo May 27 '14 at 18:24
4

If you do .AddWithValue("@P1", ...) then ParameterName already begins with an '@', so the above code tries to replace "@@P1" with the value, so it doesn't work. What am I missing? – codah Aug 10 '17 at 05:02
2

I know this is old but your code has issues. First of all, you use `command` on the first line, and `cmd` on the others. They should be the same. Second, it is not necessary to call `ToString()` on `CommandText`. It is already a string. Next, the parameter should only be enclosed in quote if it's a quotable value. Integers, for example, are not. And finally, as already pointed out, you shouldn't prepend the `@` to the parameter name as it will normally already have it. – Jonathan Wood Mar 14 '18 at 17:52

score 6 · Accepted Answer · answered Oct 14 '11 at 19:51

There's no guarantee that there is such a thing as "the query with the parameters applied". I would hope that a driver would simply send down the command as SQL and the parameters in an appropriate form to represent each value. Why go to the bother of escaping values etc, only for the query processor to unescape them and parse them at the other side? It's more efficient and less risky to just pass the data in a binary format of some description.

You should regard it as some code (the SQL) which uses some data (the parameters) and keep the two concepts very separate in your mind. If you need to log what's going on, I would log it as the parameterized SQL and the parameter values separately.

Ahh, okay, I wasn't aware of that. I thought the parameters and values were combined in the MySQL library before sending off to server, lesson learned. — Mike, Oct 14 '11 at 19:58
@Mike: It's *possible* that they are - but certainly not *necessary*, and personally I hope they're not :) — Jon Skeet, Oct 14 '11 at 20:00

score 2 · Answer 3 · answered Nov 30 '16 at 12:11

the @christopher answer was great but just string parameters will need ' (single quotation). the best is to use below method:

  private string getGeneratedSql(SqlCommand cmd)
    {
        string result = cmd.CommandText.ToString();
        foreach (SqlParameter p in cmd.Parameters)
        {
            string isQuted = (p.Value is string) ? "'" : "";
            result = result.Replace('@' + p.ParameterName.ToString(), isQuted + p.Value.ToString() + isQuted);
        }
        return result;
    }

score 2 · Answer 4 · answered Oct 14 '11 at 19:54

The parameters remain separate all the way to the server, so the query string you see is what actually goes to the server, independently from the parameters. So I think you need to deal more directly with understanding how parameterized queries work rather than trying to see what the query would look like with the parameters in place. You can use SQL trace to see the query come in. The parameters will still be separate, but it will show you the values.

My experience is with SQL Server, so I'm not sure how applicable this is to MySQL.

Thanks for your response. I didn't know the values stayed separate all the way to the server. — Mike, Oct 14 '11 at 20:00

score 1 · Answer 5 · answered Jul 23 '19 at 19:51

I use this for debuging in HTML. Must of the time is enough for testing with simple copy paste;


        public static string GetQueryHtml(string query, List<SqlParameter> parameters = null)
        {
            string _return = ""; string _parmStringValue; string _varlenght = "50";
            foreach (SqlParameter parameter in parameters)
            {
                if (parameter.SqlDbType == SqlDbType.DateTime)
                {
                    _parmStringValue = "'" + ((DateTime)parameter.Value).ToString("yyyy-MM-dd hh:mm:ss") + "'";
                    _return += Environment.NewLine +  "DECLARE " + parameter.ParameterName + " AS " + parameter.SqlDbType.ToString() + " SET " + parameter.ParameterName + " = " + _parmStringValue;
                }                 
                else if (parameter.SqlDbType == SqlDbType.NVarChar || parameter.SqlDbType == SqlDbType.Char)
                {
                    _varlenght = parameter.Value.ToString().Length.ToString();
                    _parmStringValue = "'" + parameter.Value.ToString() + "'";
                    _return += Environment.NewLine + "DECLARE " + parameter.ParameterName + " AS " + parameter.SqlDbType.ToString() + "(" + _varlenght + ") SET " + parameter.ParameterName + " = " + _parmStringValue;
                }
                else
                {
                    _return += Environment.NewLine + "DECLARE " + parameter.ParameterName + " AS " + parameter.SqlDbType.ToString() + " SET " + parameter.ParameterName + " = " + parameter.Value.ToString();
                }


            }

            return "<div><pre><code class='language-sql'>" + _return + Environment.NewLine + Environment.NewLine + query + "</code></pre></div>";

        }

score 1 · Answer 6 · answered Oct 14 '11 at 19:56

1

Not sure why you need this, but if it's for debugging purposes you can always turn on the global log on your local mysql database machine to see the query sent to the database (you don't want to turn it on on a production machine though - it might slow it down significantly).

answered Oct 14 '11 at 19:56

krakover

2,989
2
27
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It is for debugging, essentially I have a query that's not resulting in what I expect. I was hoping to just take the "final" query from the app and check it against the DB, guess I'll have to do it this way. Thanks for your response. – Mike Oct 14 '11 at 19:59

score 1 · Answer 7 · answered Oct 14 '11 at 20:03

1

If you would like to use a tool you could try using Toad for MySql which has a Profiler and you can see what is being sent to the server.

answered Oct 14 '11 at 20:03

Hanlet Escaño

17,114
8
52
75

score 0 · Answer 8 · answered Mar 12 '21 at 21:43

For anyone wanting to use Christopher's answer with Mysql, this worked for me...

string tmp = cmd.CommandText.ToString();
foreach (MySqlParameter param in cmd.Parameters)
{
    tmp = tmp.Replace(param.ParameterName.ToString(), "'" + param.Value.ToString() + "'");
}

A way to see query after parameters are applied?

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