SQL interview questions - sql

Question

Table-1
Col1 col2
11 A
26 B
31 C
43 D
Table-2
Col1 col2
16 E
46 F
39 G
42 H
And need output is
Col1 col2 Col1 col2
11 A 16 E
26 B 46 F
31 C 39 G
43 D 42 H

Answer 1

Here's one option:
SQL> with
2 -- sample data
3 a (col1, col2) as
4 (select 11, 'A' from dual union all
5 select 26, 'B' from dual union all
6 select 31, 'C' from dual union all
7 select 43, 'D' from dual
8 ),
9 b (col1, col2) as
10 (select 16, 'E' from dual union all
11 select 46, 'F' from dual union all
12 select 39, 'G' from dual union all
13 select 42, 'H' from dual
14 ),
15 -- find something to join rows on - for example, row number. Your example shows that
16 -- values are sorted by COL2
17 a2 as
18 (select col1, col2, row_number() over (order by col2) rn from a),
19 b2 as
20 (select col1, col2, row_number() over (order by col2) rn from b)
21 -- join a2 and b2 on RN
22 select a2.col1, a2.col2, b2.col1, b2.col2
23 from a2 join b2 on a2.rn = b2.rn
24 order by a2.col1;
COL1 COL2 COL1 COL2
----- ---- ----- ----
11 A 16 E
26 B 46 F
31 C 39 G
43 D 42 H
SQL>

Answer 2

select t1.col1, t1.col2, t2.col1, t2.col2 from table1 as t1
left join table2 as t2 on 1=1
Try this

Answer 3

select * from table1 t1 join table2 t2 on ascii(t1.col2)+4 = ascii(t2.col2);
Note: this only works with the specific input provided, but why not? It just goes to show that providing minimal input and expected output is not sufficient. You have to explain what rules the input should follow and what rules the processing should follow.
Littlefoot answers a different question than I do, but even he silently makes some assumptions. For example, he decided not to show any output if there are unmatched rows on one side or the other.
The correct real-world answer to this interview question would be to list the questions one would have to ask before being able to supply an appropriate answer.