TABLE X
col1,col2
1 , 2
1 , 7
1 , 4
1 , 8
2 , 3
2 , 1
2 , 2
3 , 1
3 , 8
3 , 9
3 , 4
4 , 5
4 , 3
4 , 2
4 , 8
4 , 4
I want to retrieve the col1 values that contains in the col2 the values 2 and 4
in this case it will retrieve the values 1 and 4
How can i accomplish this without using the UNION ALL operator ?
The query that i am using is
select distinct col1
from X as A
where col1 = (
select col1 from (
select distinct col1
from X as B
where A.col1 = B.col1 and col2 = 2
union ALL
select distinct col1
from X as C
where A.col1 = C.col1 and col2 = 4
) D
group by col1
having count(col1) > 1
)
It is returning the correct result but i guess is to performance expensive.
Can anyone give me ideas about how to achieve the same result but without unions ?
This problem is called Relational Division, here is one way to do so:
SELECT col1
FROM tablex
WHERE col2 IN (2, 4)
GROUP BY col1
HAVING COUNT(DISTINCT col2) >=2
The HAVING COUNT(col2) >=2 will ensure that the selected col1 must have both the two values 2 and 4 at least.
SQL Fiddle Demo
I think the best performance will come from inner joining the table with itself:
SELECT DISTINCT X1.col1
FROM X X1 INNER JOIN X X2 ON X1.col1=X2.col1
WHERE X1.col2=2 AND X2.col2=4
Related
I have a table named table1, with one column named col1, which takes value in range 1-9.
table1
col1
1
9
7
2
4
6
1
9
3
5
Now I want to add another column which maps values in col1 to another value given in a map.
1 -> A, 2 -> B, 3 -> C, 4 -> D, 5 -> E, 6 -> F, 7 -> G, 8 -> H, 9 -> I
I want results to look like below.
col1 col2
1 A
9 I
7 G
2 B
4 D
6 F
1 A
9 I
3 C
5 E
My approach is to create a new table with mapping and then do a inner join.
CREATE TABLE map (
col1 int,
col2 varchar
);
INSERT INTO map
(col1, col2)
VALUES
(1,'A'),(2,'B'),(3,'C'),(4,'D'),(5,'E'),(6,'F'),(7,'G'),(8,'H'),(9,'I');
SELECT table1.col1, map.col2
FROM table1 INNER JOIN map ON table1.col1 = map.col1
Is this efficient approach, are there better methods than this?
Use case statement:
Update t
Update new_column =
Case
WHEN col1 = 1 THEN 'A'
WHEN col1 = 2 THEN 'B'
WHEN col1 = 3 THEN 'C'
WHEN col1 = 4 THEN 'D'
WHEN col1 = 5 THEN 'E'
WHEN col1 = 6 THEN 'F'
WHEN col1 = 7 THEN 'G'
WHEN col1 = 8 THEN 'H'
WHEN col1 = 9 THEN 'I'
END
FROM table1 t
Although creating map table can be a good idea, assume you need to fill the map table with query. Then case statement is useful.
CASE col1
WHEN 1 THEN 'A'
WHEN 2 THEN 'B'
WHEN 3 THEN 'C'
WHEN 4 THEN 'D'
-- And so on
END
If I have two columns:
col1 col2 amount
1 2 15
2 3 12
1 3 10
3 1 4
3 2 3
And I perform a group by col1,col2 then I get a row for each combination (present) in the data.
My problem though is, that I dont always have all combinations, but I would want to return a row of each combination still. So if there isn't a combination. for example 2 -> 1 then I would want its value to be 0.
Can I somehow specify the "levels" of the group by?
I'm using SQL Oracle.
and the outcome I would want is:
1 -> 2 15
1 -> 3 10
2 -> 1 0
2 -> 3 12
3 -> 1 4
3 -> 2 3
With their respective amount, and 0 if they dont exist, or null works. ( I have a filter to exclude where col1 and col2 are same)
Generate all the rows using cross join and then filter for the ones you want:
select c1.col1, c2.col2, coalesce(t.amount, 0)
from (select 1 as co1l from dual union all
select 2 as co1l from dual union all
select 3 as co1l from dual
) c1 cross join
(select 1 as co12 from dual union all
select 2 as co12 from dual union all
select 3 as co12 from dual
) c2 left join
t
on t.col1 = c1.col1 and t.col2 = c2.col2
where c1.col1 <> c2.col2;
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
Let's say I have the dataset that looks like:
col1 col2 col3
a 2 20
a 3 12
a 4 34
b 2 44
c 3 23
c 5 13
....
What I want is a count of col1.
Output:
col1 col2 col3 count
a 2 20 3
a 3 12 3
a 4 34 3
b 2 44 1
c 3 23 2
c 5 13 2
.......
I know I can do by:
with cte as (
select col1, count(*) count
from tab1)
select a.col1,a.col2,a.col3,cte.count
from tab1
join cte on a.col1=cte.col1
But is there any other I can do that without cross apply or cte?
Also, assuming there are more than 3 letters in col1, so I couldn't use sum function either:
SUM(CASE WHEN ItemID = 'a' THEN 1 ELSE 0 END) AS count_a
If you're using SQL Server 2008+, you can use COUNT() OVER():
SELECT *,
COUNT(*) OVER(PARTITION BY col1)
FROM tab1
ONLINE DEMO
Consider this example table "Table1".
Col1 Col2
A 1
B 1
A 4
A 5
A 3
A 2
D 1
B 2
C 3
B 4
I am trying to fetch those values from Col1 which corresponds to all values (in this case, 1,2,3,4,5). Here the result of the query should return 'A' as none of the others have all values 1,2,3,4,5 in Col2.
Note that the values in Col2 are decided by other parameters in the query and they will always return some numeric values. Out of those values the query needs to fetch values from Col1 corresponding to all in Col2. The values in Col2 could be 11,12,1,2,3,4 for instance (meaning not necessarily in sequence).
I have tried the following select query:
select distinct Col1 from Table1 where Col1 in (1,2,3,4,5);
select distinct Col1 from Table1 where Col1 exists (select distinct Col2 from Table1);
and its different variations. But the problem is that I need to apply an 'and' for Col2 not an 'or'.
like Return a value from Col1 where Col2 'contains' all values between 1 and 5.
Appreciate any suggestion.
You could use analytic ROW_NUMBER() function.
SQL FIddle for a setup and working demonstration.
SELECT col1
FROM
(SELECT col1,
col2,
row_number() OVER(PARTITION BY col1 ORDER BY col2) rn
FROM your_table
WHERE col2 IN (1,2,3,4,5)
)
WHERE rn =5;
UPDATE As requested by OP, some explanation about how the query works.
The inner sub-query gives you the following resultset:
SQL> SELECT col1,
2 col2,
3 row_number() OVER(PARTITION BY col1 ORDER BY col2) rn
4 FROM t
5 WHERE col2 IN (1,2,3,4,5);
C COL2 RN
- ---------- ----------
A 1 1
A 2 2
A 3 3
A 4 4
A 5 5
B 1 1
B 2 2
B 4 3
C 3 1
D 1 1
10 rows selected.
PARTITION BY clause will group each sets of col1, and ORDER BY will sort col2 in each group set of col1. Thus the sub-query gives you the row_number for each row in an ordered way. now you know that you only need those rows where row_number is at least 5. So, in the outer query all you need ot do is WHERE rn =5 to filter the rows.
You can use listagg function, like
SELECT Col1
FROM
(select Col1,listagg(Col2,',') within group (order by Col2) Col2List from Table1
group by Col1)
WHERE Col2List = '1,2,3,4,5'
You can also use below
SELECT COL1
FROM TABLE_NAME
GROUP BY COL1
HAVING
COUNT(COL1)=5
AND
SUM(
(CASE WHEN COL2=1 THEN 1 ELSE 0
END)
+
(CASE WHEN COL2=2 THEN 1 ELSE 0
END)
+
(CASE WHEN COL2=3 THEN 1 ELSE 0
END)
+
(CASE WHEN COL2=4 THEN 1 ELSE 0
END)
+
(CASE WHEN COL2=5 THEN 1 ELSE 0
END))=5