I am not asking how to delete duplicates.
I want to assign unique ID for group of duplicates:
A A
A A
A B
B B
B B
A A 1
A A 1
A B 2
B B 3
B B 3
You are looking for dense_rank():
select t.*,
dense_rank() over (order by col1, col2) as newcol
from t;
Related
I have the following two tables (postgresql)
tableA
a b
----------
1 A
2 B
table B
c b
----------
1 A
3 B
I want to find out the same number of columns b, but if column a and column c are the same, count one.
So the final result should be
b count
----------
A 1
B 2
How should I write sql?
You need union all for the 2 tables and then group by b to count distinct values of a:
select t.b, count(distinct t.a) counter
from (select * from tablea union all select * from tableb) t
group by t.b
Aggregate by column b and take the distinct count of column a:
SELECT b, COUNT(DISTINCT a) AS count
FROM yourTable
GROUP BY b
ORDER BY b;
I have 2 tables like this :
table_a
id col2
1 A
1 B
2 A
2 B
3 B
table_b
id col1
1 X
2 Y
3 Z
result:
id col1 col2
1 X A_B
2 Y A_B
3 Z B
How can I achieve this?
You want listagg():
select b.id, b.col1,
listagg(a.col2, '_') within group (order by a.col2) as col2
from table_b b join
table_a a
on b.id = a.id
group by b.id, b.col1;
Let's suppose a have a very simple query in SQL
SELECT Col1,Col2 From Table1
and it gives me result:
Col1 Col2
A 5
A 7
A 2
B 1
B 1
B 4
B 0
C 4
C 1
C 2
I want to count rows in groups made by Col1 and in order made by Col2. If values in Col2 for some rows in group are equal then they should have different numbers, as shown in example
So I want to have
Col1 Col2 Nr
A 5 2
A 7 3
A 2 1
B 0 1
B 1 2
B 1 3
B 4 4
C 4 3
C 1 1
C 2 2
Any ideas how to make it?
If your database supports window functions, use ROW_NUMBER
select col1,col2,row_number() over(partition by col1 order by col2) as nr
from tablename
If your database doesn't support window functions, use
select col1,col2,
(select count(*)+1 from tablename t1 where t1.col1=t.col1 and t1.col2<t.col2) as nr
from tablename t
You can use the row_number window function:
SELECT col1,
col2,
ROW_NUMBER() OVER (PARTITION BY col1 ORDER BY col2 ASC) AS Nr
FROM table1
ORDER BY 1, 2, 3
I have to join tables in a following way:
Table A:
1
2
3
4
5
Table B:
A
B
The result table should be:
1 A
2 B
3 A
4 B
5 A
Do you have any ideas how to do this?
Assuming worst case, the column in table A is not a sequence without gaps and the number of rows in table B is not known in advance, you must apply a ROW_NUMBER on both tables and then join on a MODULO:
SELECT col1, col2
FROM
(
SELECT col1,
ROW_NUMBER() OVER (ORDER BY col1) -1 AS rn
FROM tableA
) AS A
JOIN
(
SELECT col2,
ROW_NUMBER() OVER (ORDER BY col2) -1 AS rn
FROM tableB
) AS B
ON A.rn % (SELECT COUNT(*) FROM tableB) = B.rn
Maybe something like this:
select A.nr, case when (A.nr%2=0) then b2.chr else b3.chr end letter
from A, B b2, B b3
where b2.chr = 'A' and b3.chr = 'B'
lets say I have tableA which has a col1 and tableB which has col2 with the following content:
Table A
---------
A
B
C
D
Table B
---------
1
2
3
4
I want a select statement that returns to me:
A, 1
B, 2
C, 3
D, 4
I have tried making this call:
Select tableA.col1, tableB.col2 from tableA, tableB
but it returns the following:
A, 1
B, 1
C, 1
D, 1
A, 2
..
..
etc
how can i get it to just pull back this:
A, 1
B, 2
C, 3
D, 4
Try this:
select b.val1, b.val1, c.val2 from tableA a
inner join (select ROW_NUMBER() OVER () AS RowNumber, col1 as val1 from tableA) on a.col1 = b.val1
inner join (select ROW_NUMBER() OVER () AS RowNumber, col2 as val2 from tableB) c on c.RowNumber = b.RowNumber