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POHow to pass a MySQL database function as a query parameter from c#
 

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  1. POHow to pass a MySQL database function as a query parameter from c#
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    <p>Let me explain a little.</p> <p>Image you have the flowing MySQL table:</p> <pre><code>CREATE TABLE test ( value DATETIME ); </code></pre> <p>Currently I am doing something like this:</p> <pre><code>command.CommandText = "UPDATE test SET value = ?value"; command.Parameters.AddWithValue("?value", DateTime.Now); </code></pre> <p>But the clients date/time settings are unreliable so I would like the time to be determined at the server. Something like:</p> <pre><code>command.CommandText = "UPDATE test SET value = NOW()"; </code></pre> <p>The trick is that I want to pass the "NOW()" function as a parameter to the original query. Please understand that this small example is OVERLY simplified. In reality the table has 48 columns, 7 of which are datetime, marking the date and/or time the user made a particular operation to the object the database row denotes. When the user performs a new operation to the object I read the entire row and insert it again, with a different ID of course, (Something like a poor man's revision history) so I like to keep the date/time of the old operation and insert it in the new row, but at the same time set the current date/time (as seen by the database) for the new operation.</p> <p>For simplicity lets go back to the previous example.</p> <p>As far as I can find I have two choices.</p> <pre><code>bool switch; .... command.CommandText = "UPDATE test SET value = " + switch ? "NOW()" : "?value"; command.Parameters.AddWithValue("?value", value); </code></pre> <p>OR</p> <pre><code>bool switch; .... if (switch) { command.CommandText = "SELECT NOW()"; value = Convert.ToDateTime(command.ExecuteScalar()); } command.CommandText = "UPDATE test SET value = ?value"; command.Parameters.AddWithValue("?value", value); </code></pre> <p>I don't like neater of them. Wouldn't it be neat if I could do something similar to:</p> <pre><code>command.CommandText = "UPDATE test SET value = ?value"; if (switch) { command.Parameters.AddWithValue("?value", "NOW()"); } else { command.Parameters.AddWithValue("?value", value); } </code></pre> <p>That way I would still execute the same one query.</p> <p>Waiting for your opinions on this. I will be very grateful for any help you can provide.</p>
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