How to Fix 'The variable name '@' has already been declared' Error in SQL Query Batch?

Variable Name Conflict in SQL Query Batch

When executing SQL queries, it's crucial to ensure uniqueness in variable names within a batch or stored procedure. The error "The variable name '@' has already been declared" indicates that multiple variables with the same name were defined.

To resolve this, focus on the code block provided:

private void btn_lock2_Click(object sender, EventArgs e)
{
    // ...
    for (long counter = from; counter <p>The mistake lies in repeatedly adding parameters within the loop. Instead, move the parameter creation outside the loop:</p><pre class="brush:php;toolbar:false">// Moved outside the loop
rwd.command.Parameters.Add(new SqlParameter("@LockState", SqlDbType.NVarChar));
rwd.command.Parameters.Add(new SqlParameter("@card_descr", SqlDbType.NVarChar));

for (long counter = from; counter <p>Alternatively, consider clearing the parameters within the loop:</p><pre class="brush:php;toolbar:false">for (long counter = from; counter <p>By following these recommendations, you can eliminate the error and ensure the uniqueness of variable names in your SQL queries.</p>

The above is the detailed content of How to Fix 'The variable name '@' has already been declared' Error in SQL Query Batch?. For more information, please follow other related articles on the PHP Chinese website!