How do I display 3 table from database at same HTML page using particular user id?

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I want to display from 3 different table and with particular user id. I've tried do and after run it will display HTTP status 500, and it said the problem at here :

rs = st.executeQuery("select * from tbl_totalmonday where idEmploy = '" + session.getAttribute("uidUser") + "'");
 rs = st.executeQuery("select * from tbl_totalsunday where idEmployE = '" + session.getAttribute("uidUser") + "'");
  rs = st.executeQuery("select * from tbl_totalholiday where idEmployP = '" + session.getAttribute("uidUser") + "'");

Then, I want to know the exact code how to display 3 database in one HTML page, is it impossible to do? I also try one with use executeQuery(query); but if I use this one it will give all output from database:

String query = "select * from tbl_totalmonday, tbl_totalsunday, tbl_totalholiday";
                                Statement st = con.createStatement();

                                rs = st.executeQuery(query);

If anyone know how to do the exact code to display all database take from particular user id, please help me, Thanks a lot for answering my question ^-^.

What I have tried:

<%
           Connection con;
           PreparedStatement pst;
           ResultSet rs;

           Class.forName("com.mysql.cj.jdbc.Driver");
           con = DriverManager.getConnection("jdbc:mysql://localhost:3306/attendance?zeroDateTimeBehavior=CONVERT_TO_NULL", "root", "");

           String query = "select * from tbl_totalmonday, tbl_totalsunday, tbl_totalholiday";

           Statement st = con.createStatement();

           rs = st.executeQuery("select * from tbl_totalmonday where idEmploy = '" + session.getAttribute("uidUser") + "'");
            rs = st.executeQuery("select * from tbl_totalsunday where idEmployE = '" + session.getAttribute("uidUser") + "'");
             rs = st.executeQuery("select * from tbl_totalholiday where idEmployP = '" + session.getAttribute("uidUser") + "'");

           while (rs.next()) {
               Double idEmploy = rs.getDouble("idEmploy");
               Double idEmployE = rs.getDouble("idEmployE");
               Double idEmployP = rs.getDouble("idEmployP");
       %>

Posted 8-Jun-22 17:20pm

aufa 2022

Updated 8-Jun-22 18:55pm

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OriginalGriff · Accepted Answer · 2022-06-08T18:55:00

Try using a JOIN: SQL Joins[^]

But ... Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.

When you concatenate strings, you cause problems because SQL receives commands like:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'

The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;--'

Which SQL sees as three separate commands:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';

A perfectly valid SELECT

SQL

DROP TABLE MyTable;

A perfectly valid "delete the table" command

SQL

--'

And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.

So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?