When we issue UPDATE, DELETE, and INSERT commands, we're
essentially sending data to the database. But a SELECT command
returns data that we want to use.
- So, we save that data in a ResultSet object. Thus, we need a different return type than the one provided to us in executeUpdate(), so we must use executeQuery().
- Think of a ResultSet as an ArrayList or Vector. It is a collection of data through which we can iterate.
- In our earlier example, we wanted to print out the data from each student. We used this type of loop to do so:
- There are some alternate ways to do this.
- You can supply the column number instead of column name.
- getString() will reasonably convert any data type to a String. This is a nice feature.
ResultSet rs = stmt.executeQuery("SELECT * FROM students");
ResultSet rs = stmt.executeQuery("Select * from student");
int recordNo = 0;
while(rs.next()) {
recordNo++;
%>
<tr>
<td colspan = 4>
Record # <%=recordNo%>
</td>
<tr>
<tr>
<td>Name: <%=rs.getString("name")%></td>
<td>ID: <%=rs.getString("bearcatID")%></td>
<td>Gender: <%=rs.getString("gender")%></td>
<td>Major: <%=rs.getString("major")%></td>
</tr>
<%
}
If this weren't a JSP, we could do something very similar:
ResultSet rs = stmt.executeQuery("Select * from student");
int recordNo = 0;
while(rs.next()) {
recordNo++;
System.out.println(recordNo + ": ");
System.out.println("Name: " + rs.getString("name"));
System.out.println("ID: " + rs.getString("bearcatID"));
System.out.println("Gender:" + rs.getString("gender"));
System.out.println("Major: " + rs.getString("major"));
}