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JSP for mySQL to Oracle

Posted on 2003-11-24
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Last Modified: 2010-04-01
I have a small program that is written using JSP using mySQL at the backend (development) and I am thinking to move it to Oracle (production). There are a few conversion issues and I appreciate your input and suggestions:

1. In mySQL there is auto_increment function but not in Oracle 9i. In my JSP sql (that uses mySQL) I could have just use

insert into t_emp (id, name) value ('', 'Joe Black');

In oracle I uses sequence and the sql looks like:

insert into t_emp values (emp_seq.nextval, 'Joe Black');

How could I use just 1 type of sql for both databases?

2. If I use NOW() in the DATETIME in mySQL in some INSERT statement, what should I replace with in Oracle? sysdate seems to be doing the equivalent.

My real questions is, using JSP, how could I program in such a way that my program is independent of the database at the backend?

Thank you.
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Question by:Tuan_Jean
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7 Comments
 
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Accepted Solution

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jarasa earned 40 total points
ID: 9816699
Hi Tuan_Jean.

I guess is not a way that you could do that, unless that you uses the DB as a parameter and put it on the the code. Different DBs uses different sentences or functions so you have to take care of them. is like the AS on the FROM statement you can't use it in Oracle but you must use it in mySQL.

If you have a way to Know the DB uses just make a switch on the code and send the proper statement to the DB.

regards

Javier
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Author Comment

by:Tuan_Jean
ID: 9820993
Thank you.
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LVL 6

Expert Comment

by:jarasa
ID: 9823162
Hi Tuan_Jean.
Did you solve the problem as I recomended you?
If you did I wonder why you assigned me a C grade instead an A grade.
regards
Javier.
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Author Comment

by:Tuan_Jean
ID: 9828184
Javier,

I understand the method you recommended are working but didn't use it as this makes the code very complex as each sql statement will have to had a switch.

However, I am not sure how the Grade C comes into the picture. I am happy to assign grade A. How do I do it?
0
 
LVL 6

Expert Comment

by:jarasa
ID: 9830715
HI Tuan_Jean.

Actually there is a way that you could do it without a switch, if you place a session variable with the DB used onces you start the application you could have a constants file with all your querys for the different DataBase and use them as needed compounding them at runtime on the JSP, somethin like this.

constants.java
public class Constants
{

    public Constants()
    {
    }

    public static final String [] ORACLE = {"ORACLE SQL 1","ORACLE SQL 2"};
    public static final String [] mySQL = {"mySQL SQL 1","mySQL SQL 2"};
   
    public String get(String s, int n) {
          String p;
             // You can make a switch here if you have more than 2 DBs
          if(s.equals("ORACLE"))
                p = this.ORACLE[n];
          else
                p = this.mySQL[n];
          return p;
          
    }
}

access.jsp
<%@ page import="Constants" %>
<%
session.putValue("DB", "ORACLE"); // Obviously you must put this in the login jsp
Constants c = new Constants();
String sql = c.get((String) session.getAttribute("DB"),0);
......
%>
<html>
<head>
<title>Documento sin t&iacute;tulo</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>

<body>
<%=sql%>
</body>
</html>


About the A grade I thisk you shoud just post a comment to the sdministrators saying that you want the Grade changed for this question from C to A.

regards.
Javier
0
 

Author Comment

by:Tuan_Jean
ID: 9833844
Javier. Thank you again.
0
 

Author Comment

by:Tuan_Jean
ID: 9833850
Dear Administrator, I am very please with the answer Javier posted. Could you please change the grade from C to A. Thank you.
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