I have 4 columns a ,b ,c, d
sample data
a | b | c | d |
1 | 1 | 101 | 0
2 | 1 | 101 | 0
3 | 1 | 101 | 1
4 | 1 | 102 | 0
5 | 1 | 102 | 0
1 | 2 | 101 | 0
2 | 2 | 101 | 1
Write a SQL command such that it should return those rows where for every value of c in b, return rows with maximum a
i.e
Expect output
a | b | c | d |
3 | 1 | 101 | 1
5 | 1 | 102 | 0
2 | 2 | 101 | 1
You can use a correlated subquery:
select t.*
from t
where t.a = (select max(t2.a) from t t2 where t2.b = t.b and t2.c = t.c);
With an index on t(b, c, a), this often has the best performance.
An alternative is window functions:
select t.*
from (select t.*, row_number() over (partition by b, c order by a desc) as seqnum
from t
) t
where seqnum = 1;
You don't mention the database you are using. In PostgreSQL you can do:
select distinct on (b, c) a, b, c, d
from t
order by b, c, a desc
Related
I have table like this
|-------------------------|
| A | B | C |
|-------------------------|
| 1 | 2 | 5 |
|-------------------------|
| 1 | 2 | 10 |
|-------------------------|
| 1 | 2 | 2 |
|-------------------------|
I need to delete all duplicated rows with equals A nad B value and lower C value
after running sql script i need to have only this row with top C Value for every equals A and B columns
|-------------------------|
| A | B | V |
|-------------------------|
| 1 | 2 | 10 |
|-------------------------|
One method is window functions:
select t.*
from (select t.*,
row_number() over (partition by a, b order by v desc) as seqnum
from t
) t
where seqnum = 1;
This returns the entire row, which can be handy if you want additional columns. If you really need just the three columns, then aggregation does what you want:
select a, b, max(v)
from t
group by a, b;
In standard SQL, you can keep only the maximum value using:
delete from t
where t.v < (select max(t2.v) from t t2 where t2.a = t.a and t2.b = t.b);
I am not sure of the logic required to accomplish this, but I want to take a table like this...
+----+------+
| Id | Type |
+----+------+
| 10 | A |
| 10 | B |
| 10 | C |
| 20 | A |
| 20 | C |
+----+------+
...and end up with a table like this...
+----+------+---+---+---+
| Id | Type | A | B | C |
+----+------+---+---+---+
| 10 | A | 1 | 1 | 1 |
| 10 | B | 1 | 1 | 1 |
| 10 | C | 1 | 1 | 1 |
| 20 | A | 1 | 0 | 1 |
| 20 | C | 1 | 0 | 1 |
+----+------+---+---+---+
...where each Id will have new columns created to consolidate information about Type into every row of that Id. Since 10 has a row of types A, B, and C, then all rows that have an ID of 10 should have a 1/true in the new columns A, B and C.
I know how to do this on a per-row basis, but can't wrap my head around how to consolidate the information from multiple rows into each row of the same ID.
Try this below logic- Demo
SELECT *,
(SELECT COUNT(DISTINCT Type) FROM your_table B WHERE B.ID = A.Id and B.Type = 'A') A,
(SELECT COUNT(DISTINCT Type) FROM your_table C WHERE C.ID = A.Id and C.Type = 'B') B,
(SELECT COUNT(DISTINCT Type) FROM your_table D WHERE D.ID = A.Id and D.Type = 'C') C
FROM your_table A
And just another option- Demo
SELECT *,
SUM(CASE WHEN Type= 'A' THEN 1 ELSE 0 END) OVER(PARTITION BY Id) A,
SUM(CASE WHEN Type= 'B' THEN 1 ELSE 0 END) OVER(PARTITION BY Id) B,
SUM(CASE WHEN Type= 'C' THEN 1 ELSE 0 END) OVER(PARTITION BY Id) C
FROM your_table
I have to perform a query where I can count the number of distinct codes per Id.
|Id | Code
------------
| 1 | C
| 1 | I
| 2 | I
| 2 | C
| 2 | D
| 2 | D
| 3 | C
| 3 | I
| 3 | D
| 4 | I
| 4 | C
| 4 | C
The output should be something like:
|Id | Count | #Code C | #Code I | #Code D
-------------------------------------------
| 1 | 2 | 1 | 1 | 0
| 2 | 3 | 1 | 0 | 2
| 3 | 3 | 1 | 1 | 1
| 4 | 2 | 2 | 1 | 0
Can you give me some advise on this?
This answers the original version of the question.
You are looking for count(distinct):
select id, count(distinct code)
from t
group by id;
If the codes are only to the provided ones, the following query can provide the desired result.
select
pvt.Id,
codes.total As [Count],
COALESCE(C, 0) AS [#Code C],
COALESCE(I, 0) AS [#Code I],
COALESCE(D, 0) AS [#Code D]
from
( select Id, Code, Count(code) cnt
from t
Group by Id, Code) s
PIVOT(MAX(cnt) FOR Code IN ([C], [I], [D])) pvt
join (select Id, count(distinct Code) total from t group by Id) codes on pvt.Id = codes.Id ;
Note: as I can see from sample input data, code 'I' is found in all of Ids. Its count is zero for Id = 3 in the expected output (in the question).
Here is the correct output:
DB Fiddle
I have a table with data like the following
key | A | B | C
---------------------------
1 | x | 0 | 1
2 | x | 2 | 0
3 | x | NULL | 4
4 | y | 7 | 1
5 | y | 3 | NULL
6 | z | NULL | 4
And I want to merge the rows together based on column A with largest primary key being the 'tie breaker' between values that are not NULL
Result
key | A | B | C
---------------------------
1 | x | 2 | 4
2 | y | 3 | 1
3 | z | NULL | 4
What would be the best way to achieve this assuming my data is actually 40 columns and 1 million rows with an unknown level of duplications?
Using ROW_NUMBER and conditional aggregation:
SQL Fiddle
WITH cte AS(
SELECT *,
rnB = ROW_NUMBER() OVER(PARTITION BY A ORDER BY CASE WHEN B IS NULL THEN 0 ELSE 1 END DESC, [key] DESC),
rnC = ROW_NUMBER() OVER(PARTITION BY A ORDER BY CASE WHEN C IS NULL THEN 0 ELSE 1 END DESC, [key] DESC)
FROM tbl
)
SELECT
[key] = ROW_NUMBER() OVER(ORDER BY A),
A,
B = MAX(CASE WHEN rnB = 1 THEN B END),
C = MAX(CASE WHEN rnC = 1 THEN C END)
FROM cte
GROUP BY A
I need a solution for the below senario
I have a table temp with columns: a, b, c, d and the data looks like this:
TABLE TEMP
+---+----+----+----+
|a | b | c | d |
+===+====+====+====+
| 1 | 1 | 1 | m |
| 1 | 2 | 1 | d |
| 1 | 3 | 1 | w |
| 2 | 1 | 1 | m |
| 2 | 2 | 1 | d |
| 2 | 2 | 1 | w |
+---+----+----+----+
QUERY
SELECT CASE WHEN B=1 AND C=1 THEN D END as T1,
CASE WHEN B=2 AND C=1 THEN D END as T2,
CASE WHEN B=3 AND C=1 THEN D END as T3
FROM TEMP
WHERE A=1
The above query gives multiple rows with null values where value is not present
I need a result set with a single row that looks like this:
Expected Result
+------+-------+------+
| T1 | T2 | T3 |
+======+=======+======+
| m | d | w |
+------+-------+------+
Do like this (using CTE)
QUERY
WITH
CTE1 as (select top 1 d as T1 from temp where b=1 and c=1),
CTE2 as (select top 1 d as T2 from temp where b=2 and c=1),
CTE3 as (select top 1 d as T3 from temp where b=3 and c=1)
select CTE1.*, CTE2.*, CTE3.*
FROM CTE1 CROSS JOIN CTE2 CROSS JOIN CTE3
SQL fiddle
About the multiple CTE
Please let me whether it works!