Can not get data from column in table when value "" - sql

Question

I have a prolem in my project when i get value from column in table. I create database by c# code.
This is my code:
public static int typeTransactionIncome = 1; // thu
public static int typeTransactionExpense = 2; // chi
public static int typeTransactionDebt = 3; // nợ
public static int typeTransactionLoan = 4; // cho vay
public static string tableNameCategory = "categories";
private static string createTableTransactionString = "CREATE TABLE IF NOT EXISTS \"transactions\" " + "(\"id\" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL ,"
+ "\"name\" VARCHAR(140) ," + "\"amount\" FLOAT NOT NULL DEFAULT (0) ," + "\"type\" INTEGER NOT NULL ,"
+ "\"created_date\" DATETIME NOT NULL DEFAULT (CURRENT_DATE) ," + "\"displayed_date\" DATETIME NOT NULL DEFAULT (CURRENT_DATE) ,"
+ "\"cat_id\" INTEGER NOT NULL DEFAULT (0) ," + "\"with_person\" VARCHAR(50)," + "\"remind_date\" DATETIME,"
+ "\"remind_num\" INTEGER DEFAULT (0) ," + "\"note\" VARCHAR(140) ," + "\"status\" BOOL NOT NULL DEFAULT (0),"
+ "\"user_id\" INT NOT NULL DEFAULT (1))";
This is insert code: Insert some column, and there 2 insert menthod
public void insertNewIncome(string _name, string _note, double _amount, DateTime _displayedDate, int _catId, int _usertId)
{
try
{
openConnection();
SqliteCommand cmd = conn.CreateCommand();
cmd.CommandText = "INSERT INTO " + tableNameTransaction + "(type, name, note, amount, displayed_date, cat_id, user_id) values (#type, #name, #note, #amount, #displayed_date, #cat_id, #user_id)";
cmd.Parameters.Add("#type", typeTransactionIncome);
cmd.Parameters.Add("#name", _name);
cmd.Parameters.Add("#note", _note);
cmd.Parameters.Add("#amount", _amount);
cmd.Parameters.Add("#displayed_date", _displayedDate);
cmd.Parameters.Add("#cat_id", _catId);
cmd.Parameters.Add("#user_id", _usertId);
cmd.ExecuteNonQuery();
//MessageBox.Show("income");
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
finally
{
closeConnection();
}
}
public void insertNewDebt(string _debter, string _note, double _amount, DateTime _ngay_vay, DateTime _ngay_tra, int _user_id)
{
try
{
openConnection();
SqliteCommand cmd = conn.CreateCommand();
cmd.CommandText = "INSERT INTO " + tableNameTransaction + "(type, with_person, note, amount, displayed_date, remind_date, user_id) VALUES (#type, #with_person, #note, #amount, #displayed_date, #remind_date, #user_id)";
cmd.Parameters.Add("#type", typeTransactionDebt);
cmd.Parameters.Add("#with_person", _debter);
cmd.Parameters.Add("#note", _note);
cmd.Parameters.Add("#amount", _amount);
cmd.Parameters.Add("#displayed_date", _ngay_tra);
cmd.Parameters.Add("#remind_date", _ngay_tra);
cmd.Parameters.Add("#user_id", _user_id);
cmd.ExecuteNonQuery();
//MessageBox.Show("debt");
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
finally
{
closeConnection();
}
}
I was insert some records to table by insertNewDebt and insertNewIncome menthod, it was ok, not any error.
This is menthod that get all record in table:
public List<ItemTransaction> loadTransactionAll(DateTime _start_date, DateTime _end_date, int _user_id)
{
List<ItemTransaction> li = new List<ItemTransaction>();
openConnection();
SqliteCommand cmd = conn.CreateCommand();
cmd.CommandText = "SELECT transactions.id AS master_id,transactions.name,transactions.amount,transactions.type,transactions.created_date, transactions.displayed_date,transactions.cat_id, transactions.with_person,transactions.remind_date,remind_num, transactions.note,transactions.status,transactions.user_id,categories.id,categories.name,categories.icon,categories.type,IFNULL(sub_amount,0) AS sub_amount "
+ "FROM transactions "
+ "LEFT JOIN categories ON transactions.cat_id = categories.id "
+ "LEFT JOIN ("
+ "SELECT sub_trans_id, IFNULL(SUM(sub_amount),0) AS sub_amount "
+ "FROM (SELECT trans_id AS sub_trans_id,SUM(amount) AS sub_amount "
+ "FROM sub_transactions "
+ "WHERE type = #type_income "
+ "GROUP BY sub_trans_id "
+ "UNION ALL SELECT trans_id AS sub_trans_id,SUM(amount) * -1 AS sub_amount "
+ "FROM sub_transactions "
+ "WHERE type = #type_expense GROUP BY sub_trans_id) GROUP BY sub_trans_id) ON sub_trans_id = master_id "
+ "WHERE (displayed_date BETWEEN #start_date AND #end_date) "
+ "AND transactions.user_id = #user_id "
+ "ORDER BY displayed_date DESC, transactions.type ASC, status ASC";
cmd.Parameters.Add("#type_income", DatabaseProccess.typeTransactionIncome);
cmd.Parameters.Add("#type_expense", DatabaseProccess.typeTransactionExpense);
cmd.Parameters.Add("#start_date", _start_date);
cmd.Parameters.Add("#end_date", _end_date);
cmd.Parameters.Add("#user_id", _user_id);
SqliteDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
ItemTransaction item = new ItemTransaction();
item.master_id = reader.GetInt32(0);
item.name = reader.GetString(1);
item.amount = reader.GetDouble(2);
item.type = reader.GetInt32(3);
item.created_date = reader.GetDateTime(4);
item.displayed_date = reader.GetDateTime(5);
item.cat_id = reader.GetInt32(6);
item.with_person = reader.GetString(7);
item.remind_date = reader.GetDateTime(8);
item.remind_num = reader.GetInt32(9);
item.note = reader[10].ToString();
item.status = reader.GetBoolean(11);
item.user_id = reader.GetInt32(12);
item.setCategory(reader.GetInt32(13), reader.GetString(14), reader.GetString(15), reader.GetInt32(16));
item.sub_amount = reader.GetDouble(17);
li.Add(item);
}
return li;
}
But when i execute insert:
insertNewIncome("", "note", "1000", DateTime.Today, 1, 1);
with 'name' field value = ""
I can not read 'name' field. Debug say:
view error screen shot here, please
And this is ItemTransaction class:
view ItemTransaction class here, please
I don't understand this error.
Please, thank

Answer 1

You're getting this error because name is NULL.
The following if statement would fix this:
if (reader(1) != null){
item.name = reader.GetString(1);
}
However if you're passing the value "", then this shouldn't be stored as NULL.
Check your database and see what the value is. Perhaps you have a trigger in place which updates "" to null.