Question

Similar question to:
Strange problem with JDBC, select returns null
but people didn’t ask for this.

My code:

public int myMethod(String day) throws SQLException{
  String sql = "Select count(*) from MyTable WHERE someColumn = " + day;
  Connection connection = ConnFactory.get();
  PreparedStatement prepareStatement = null;
  ResultSet resultSet = null;
  int ret = -1;
  try{
      prepareStatement = connection.prepareStatement(sql);
      resultSet = prepareStatement.executeQuery(sql);
      if(resultSet.next()){
          ret = resultSet.getInt(1);
      }
  }
  catch(SQLException sqle){
      // closing statement & ResultSet, log and throw exception
  }
  finally{
     // closing statement & ResultSet
  }
  ConnFactory.kill(connection);

  return ret;
}

This code always return 0. I try to log sql before execution and try to run it in SQLdeveloper and get correct value (over 100).
When I remove WHERE, sql = "Select count(*) from MyTable query return number of all rows in table.
I use Oracle 10g with ojdbc-14.jar (last version from maven repo) and Java 6.

Answer 1

day has not been quoted correctly, I would suggest using a prepared statement like a prepared statement as follows:

...
try {
    prepareStatement = connection.prepareStatement("Select count(*) from MyTable WHERE someColumn = ?");
    prepareStatement.setString(1,day);
...

is the same as:

sql = "Select count(*) from MyTable WHERE someColumn = '" + day + "'";

with several advantages over the latter (mainly security and performance). See:

http://java.sun.com/docs/books/tutorial/jdbc/basics/prepared.html