using ResultSet when row value from database is NULL

Question

When querying the database directly, result is NULL, now Im using ResultSet to check if result is NULL, do something else, if result is not NULL, print the result: This my COde:

if(rs4 != null) {
            while(rs4.next()) {
            String ad =rs4.getString("number");                    
            System.out.println(ad);
            }
        }
        else{
            System.out.println("ZERO ENTRIES");
        }`

Database row value is NULL,since there is no row returned from my query so definitely i expect the else statement to run, but now the if statement is still being excecuted and prints null

Even if there are no results, rs4 should still not be null (unless your code does something strange). — Steve Smith, Apr 05 '17 at 15:18
Assuming you are using `Statement`and `executeQuery` , it returns : "a `ResultSet` object that contains the data produced by the given query; _never null_" — Arnaud, Apr 05 '17 at 15:19
Possible duplicate of [Java ResultSet how to check if there are any results](http://stackoverflow.com/questions/867194/java-resultset-how-to-check-if-there-are-any-results) — Arnaud, Apr 05 '17 at 15:28
@steveSmith oh, okay, coz it prints true, so I need to check the value from the number collumn that is returned, it is supposed to be some numbers, but since i have no data for the selected query, it is empty. How do I go around that and print something different.... — Beroo, Apr 05 '17 at 15:43

score 1 · Answer 1 · answered Apr 05 '17 at 15:20

1

What you see as NULL when querying the DB directly is the value of the column number, not the value of the row.

so, that's why you get a non-null row with a NULL value in number column in your ResultSet.

answered Apr 05 '17 at 15:20

alayor

4,537
6
27
47

oh, so how can I restructure my code to cater for that outcome? – Beroo Apr 05 '17 at 15:28

score 0 · Answer 2 · answered Apr 05 '17 at 15:28

0

You can use something like:

if (!resultSet.isBeforeFirst() ) {    
    System.out.println("No data"); 
}

Or:

if (!resultSet.next() ) {
    System.out.println("no data");
}

answered Apr 05 '17 at 15:28

dcalap

1,048
2
13
37

as states by @alayor above, the row value returned is `NULL`, meaning there is something being returned, and I need a way to get past that. Row value is expected to be numbers, digits, and when empty, it should be `null` as expected, ....I want to get around that `null` aspect and print something else – Beroo Apr 05 '17 at 15:32
https://docs.oracle.com/javase/7/docs/api/java/sql/ResultSet.html#wasNull() this maybe helps... – dcalap Apr 05 '17 at 15:33

score 0 · Answer 3 · answered Apr 05 '17 at 18:00

I finally found a way to go around it. Using rs.getInt() this will return 0 whenever row value is NULL and return new row value , whenever there is a row found.

This solved it :-)

while(rs.next())
        {
            // using rs.getInt() will return zero when row value from your query is NULL
            int i = rs.getInt("number");
            if(i<0) //check if zero
            {
                // When result is NULL i =0
                System.out.println("your value");
            }else{
                //When there are rows found from database i > 0
                String ad=rs.getString("number");
                System.out.println(ad);
            }
        }`

using ResultSet when row value from database is NULL

3 Answers3