这个Java JDBC程序有什么问题？

Question

What is wrong in this Java JDBC program?

I have written a method that takes a ResultSet and prints all of its records.

My SQL query is:

Set @counter := 0, @counterQty := 0, @counterAvb := 0, @counterIss := 0, @counterRep := 0 ,@counterDes := 0;
Select *
From (SELECT 
       (Select (@counter := (@counter + 1) ) ) 'Sr.No.',
       testt.BookName,
       testt.BookQty,
       testt.Code, 
       testt.Available, 
       testt.Issued, 
       testt.Repair, 
       testt.Destroyed,
       (@counterQty := @counterQty + testt.BookQty ) TotalQty,
       (@counterAvb := @counterAvb + testt.Available ) TotalAvb,
       (@counterIss := @counterIss + testt.Issued ) TotalIss,   
       (@counterRep := @counterRep + testt.Repair ) TotalRep,   
       (@counterDes := @counterDes + testt.Destroyed ) TotalDest
     From (Select a.b_name BookName, a.b_qty BookQty, a.b_acc_id Code,
            SUM(case  when b.status='A' then 1 else 0 end) as Available,
            SUM(case  when b.status='I' then 1 else 0 end) as Issued, 
            SUM(case  when b.status='R' then 1 else 0 end) as Repair, 
            SUM(case  when b.status='D' then 1 else 0 end) as Destroyed      
          From tbl_book_info a left join tbl_books b on a.b_acc_id = b.accid 
          GROUP BY a.b_name, a.b_qty, a.b_acc_id order by a.b_acc_id
     )testt
)Main;

When I am executing this query in MySQL Workbench, it returns:

    +--------+--------------+---------+-------+-----------+--------+--------+-----------+----------+----------+----------+----------+-----------+
    | Sr.No. | BookName     | BookQty | Code  | Available | Issued | Repair | Destroyed | TotalQty | TotalAvb | TotalIss | TotalRep | TotalDest |
    +--------+--------------+---------+-------+-----------+--------+--------+-----------+----------+----------+----------+----------+-----------+
    |      1 | Java book    |       3 | 10001 |         0 |      0 |      1 |         2 |        3 |        0 |        0 |        1 |         2 |
    |      2 | Cpp Book     |       5 | 10002 |         3 |      1 |      0 |         1 |        8 |        3 |        1 |        1 |         3 |
    |      3 | Cpp 1.17     |       5 | 10003 |         3 |      1 |      0 |         1 |       13 |        6 |        2 |        1 |         4 |
    |      4 | Visual Basic |       4 | 10004 |         4 |      0 |      0 |         0 |       17 |       10 |        2 |        1 |         4 |
    +--------+--------------+---------+-------+-----------+--------+--------+-----------+----------+----------+----------+----------+-----------+
    4 rows in set (0.25 sec)

But when I am executing this query in Java and printing all data of ResultSet, it returns like:

        1       2               3         4         5           6       7         8         9           10          11        12          13                    
    +--------+--------------+---------+-------+-----------+--------+--------+-----------+----------+----------+----------+----------+-----------+
    | Sr.No. | BookName     | BookQty | Code  | Available | Issued | Repair | Destroyed | TotalQty | TotalAvb | TotalIss | TotalRep | TotalDest |
    +--------+--------------+---------+-------+-----------+--------+--------+-----------+----------+----------+----------+----------+-----------+

       0       Cpp 1.17          5       10003          3     1          0          1          0          0          0          0          0

       0       Cpp Book          5       10002          3     1          0          1          0          0          0          0          0

       0       Java book         3       10001          0     0          1          2          0          0          0          0          0

       0       Visual Basic      4       10004          4     0          0          0          0          0          0          0          0

    +--------+--------------+---------+-------+-----------+--------+--------+-----------+----------+----------+----------+----------+-----------+

My question is:

Tables structure

create table if not exists tbl_book_info(
    b_acc_id int(5) not null auto_increment,
    b_name varchar(50) not null,
    b_qty int(2) not null,
    b_type varchar(30) not null,
    b_auth1 varchar(50) not null,
    b_auth2 varchar(50),
    b_pub varchar(50) not null,
    b_pages int(4) not null,
    b_rack int(5) not null,
    b_price  Decimal(6,2) not null,
    b_about text,
    primary key(b_acc_id)
);

create table if not exists tbl_books(   
    accid int(5) references tbl_book_info.b_acc_id,
    accno int(3),
    status varchar(1) default "A",
    primary key(accid,accno)
);

My code to print this:

Connection con = getDbConnObj();
Statement st = con.createStatement();
ResultSet rs = st.executeQuery( sql );
printRsLast(rs);

public void printRsLast(ResultSet rs){
/*  +---1----+-----2--------+----3----+--4----+-----5-----+----6---+---7----+-----8-----+-----9----+----10----+----11----+----12----+-----13----+
    | Sr.No. | BookName     | BookQty | Code  | Available | Issued | Repair | Destroyed | TotalQty | TotalAvb | TotalIss | TotalRep | TotalDest |
rs= +--------+--------------+---------+-------+-----------+--------+--------+-----------+----------+----------+----------+----------+-----------+
    |      1 | Java book    |       3 | 10001 |         1 |      0 |      0 |         2 |        3 |        1 |        0 |        0 |         2 |
    |...........................................................................................................................................|
    |...........................................................................................................................................|
    |...........................................................................................................................................|
    +--------+--------------+---------+-------+-----------+--------+--------+-----------+----------+----------+----------+----------+-----------+   */


    String separator = "          ";
    try{
        rs.beforeFirst();
        int n=0;

        p("$$$ RS Attr. are : \n\n Sr.No. | BookName     | BookQty | Code  | Available | Issued | Repair | Destroyed | TotalQty | TotalAvb | TotalIss | TotalRep | TotalDest , Row are...\n");

        while(rs.next()){
            n++;
            String nm , m;

            m = rs.getInt(1)+ separator + rs.getString(2)+ separator + rs.getInt(3)+ separator + rs.getInt(4)+ separator + rs.getInt(5)+ separator + rs.getInt(6)+ separator + rs.getInt(7)+ separator + rs.getInt(8)+ separator + rs.getInt(9)+ separator + 
                rs.getInt(10)+ separator + rs.getInt(11)+ separator + rs.getInt(12)+ separator + rs.getInt(13);
            p(m+"\n");
        }
        p("\nTotal Rows = "+n);
    } catch(Exception e){
        p("\n!!! Excep in 'printRsLast(ResultSet rs), msg = '"+e.getMessage());
    }
}

public Connection getDbConnObj() {
    // Creating 'Connection' class' Reference Variable ...
    Connection con = null;
    String url = "jdbc:mysql://localhost:3306/librarydb";
    String dbUname = "root";
    String dbPass = "";
    try {
        Class.forName("com.mysql.cj.jdbc.Driver");
        con = DriverManager.getConnection(url, dbUname, dbPass);
    } catch (Exception e) {
        con = null;
    } finally {
        return con;
    }
}

I tried both the things ...

1)

sql = "Set @counter := 0...";
    rs = st.execute(sql);       //  Execute this 'Set @counter...' Stmt first Than

    sql = "Select * From...";
    rs = st.executeQuery(sql);  //  Executing this 'Select * from...' Stmt to get the Tabular Data...
    printRsLast(rs);

2)

  sql = "Set @counter := 0...
            ....
            ....
            )Main;" 
    rs = st.executeQuery(sql);  //  Executing these Entire Stmt to get the Tabular Data...
    printRsLast(rs);

Answer 1

You haven't shown us how you've constructed the string sql in your Java code, so I'm going to have to guess.

It seems that sql contains your query from Select * onwards, without the line Set @counter := 0 ... . I was able to reproduce your output if I set sql to this. Perhaps you've tried putting that Set line in the query as well and that generated an error so you took it out?

What you need to do instead is to execute the Set @counter := 0 ... line and then run the query. In other words, replace the lines

Connection con = getDbConnObj();
Statement st = con.createStatement();
ResultSet rs = st.executeQuery( sql );
printRsLast(rs);

with

Connection con = getDbConnObj();
Statement st = con.createStatement();
st.execute("Set @counter := 0 ...");
ResultSet rs = st.executeQuery( sql );
printRsLast(rs);

I made this modification to your code and it generated the output you wanted.