Selecting specific records in a SQL Server database from C#

Question

I am currently trying to grab some rows from a SQL Server database using C# that are of the following criteria:

• From the RamResults database
• in the Results table
• where the Date column is equal to the current date

I have the following so far:

// Open the same connection with the same connection string.
using (SqlCeConnection con = new SqlCeConnection(DatabaseControl.conString))
{
   con.Open();
   // Read specific values in the table.
   using (SqlCeCommand com = new SqlCeCommand("SELECT Result FROM RamResults WHERE Date == @Form1.date", con))
   {
      SqlCeDataReader reader = com.ExecuteReader();
      while (reader.Read())
      {
         int resultsoutput = reader.GetInt32(0);
         MessageBox.Show(resultsoutput.ToString());
      }
   }
}

Using SELECT Result FROM RamResults WHERE Date == Form1.date throws an error:

There was an error parsing the query. [ Token line number = 1,Token line offset = 43,Token in error = = ]

Although if I take out the WHERE statement e.g.

SELECT Result FROM RamResults

it works perfectly

Solution 1

Description

2 things

1. Use = instead of == because this is the right equals operator in T-SQL. Your Query should be like this

   SELECT Result FROM RamResults WHERE Date = @Date

2. You forget to pass in the parameter.

Sample

// Open the same connection with the same connection string.
using (SqlCeConnection con = new SqlCeConnection(DatabaseControl.conString))
{
    con.Open();
    // Read specific values in the table.
    using (SqlCeCommand com = new SqlCeCommand("SELECT Result FROM RamResults WHERE Date = @Date", con))
    {
        com.Parameters.AddWithValue("@Date", Form1.date);
        SqlCeDataReader reader = com.ExecuteReader();
        while (reader.Read())
        {
            int resultsoutput = reader.GetInt32(0);
            MessageBox.Show(resultsoutput.ToString());
        }
    }
}

Solution 2

Try parameterizing your query and replace == with = in your WHERE clause:

// ...
using (SqlCeCommand com = 
    new SqlCeCommand("SELECT Result FROM RamResults WHERE Date = @date", con))
{
    com.Parameters.Add(new SqlParameter("date", Form1.date));
    // ...
}
// ...

Solution 3

Try this:

using (SqlCeCommand com = new SqlCeCommand("SELECT Result FROM RamResults WHERE Date = @date", con))
    {
        com.Parameters.AddWithValue("date",Form1.date);
        SqlCeDataReader reader = com.ExecuteReader();
        while (reader.Read())

Always use SQL parameters instead of string concatenation.

Solution 4

Not ==, use = for equation in SQL:

WHERE Date = @Form1.date

Solution 5

The operator "==" is invalid syntax for SQL. Use a single equal sign "=" in the where clause.

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