The following questions are based on the tables ‘test1’: select * from test1; tt
ID: 3597052 • Letter: T
Question
The following questions are based on the tables ‘test1’:
select * from test1;
tt | discount
------------------------------------
14 | 0.00
9999 | 0.00
10 | 22.22
11 | 0.00
null | 11.00
(5 rows)
Write down the results of executing the following
1) select count(*) from test1;
2) select count(tt) from test1;
3) select count(distinct discount) from test1;
4) select avg(tt) from test1;
5) select avg(distinct discount) from test1;
6) select * from test1 t1 natural inner join test1 t2;
Explanation / Answer
1) 5
2) 5
3) 3
4) 206.8
5) 11.733
6)
t1.tt | t1.discount t2.tt | t2.discount
----------------------------------------------------------------------------
14 | 0.00 14 | 0.00
9999 | 0.00 14 | 0.00
10 | 22.22 14 | 0.00
11 | 0.00 14 | 0.00
null | 11.00 14 | 0.00
14 | 0.00 9999 | 0.00
9999 | 0.00 9999 | 0.00
10 | 22.22 9999 | 0.00
11 | 0.00 9999 | 0.00
null | 11.00 9999 | 0.00
14 | 0.00 10 | 22.22
9999 | 0.00 10 | 22.22
10 | 22.22 10 | 22.22
11 | 0.00 10 | 22.22
null | 11.00 10 | 22.22
14 | 0.00 11 | 0.00
9999 | 0.00 11 | 0.00
10 | 22.22 11 | 0.00
11 | 0.00 11 | 0.00
null | 11.00 11 | 0.00
14 | 0.00 null | 11.00
9999 | 0.00 null | 11.00
10 | 22.22 null | 11.00
11 | 0.00 null | 11.00
null | 11.00 null | 11.00
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