I have a group by query which fetches me some records. What if I wish to find other column details representing those records.
Suppose I have a query as follows .Select id,max(date) from records group by id;
to fetch the most recent entry in the table.
I wish to fetch another column representing those records .
I want to do something like this (This incorrect query is just for example) :
Select type from (Select id,max(date) from records group by id) but here type doesnt exist in the inner query.
I am not able to define the question in a simpler manner.I Apologise for that.
Any help is appreciated.
EDIT :
Column | Type | Modifiers
--------+-----------------------+-----------
id | integer |
rdate | date |
type | character varying(20) |
Sample Data :
id | rdate | type
----+------------+------
1 | 2013-11-03 | E1
1 | 2013-12-12 | E1
2 | 2013-12-12 | A3
3 | 2014-01-11 | B2
1 | 2014-01-15 | A1
4 | 2013-12-23 | C1
5 | 2014-01-05 | C
7 | 2013-12-20 | D
8 | 2013-12-20 | D
9 | 2013-12-23 | A1
While I was trying something like this (I'm no good at sql) : select type from records as r1 inner join (Select id,max(rdate) from records group by id) r2 on r1.rdate = r2.rdate ;
or
select type from records as r1 ,(Select id,max(rdate) from records group by id) r2 inner join r1 on r1.rdate = r2.rdate ;
You can easily do this with a window function:
SELECT id, rdate, type
FROM (
SELECT id, rdate, type, rank() OVER (PARTITION BY id ORDER BY rdate DESC) rnk
FROM records
WHERE rnk = 1
) foo
ORDER BY id;
The window definition OVER (PARTITION BY id ORDER BY rdate DESC) takes all records with the same id value, then sorts then from most recent to least recent rdate and assigns a rank to each row. The rank of 1 is the most recent, so equivalent to max(rdate).
If I've understood the question right, then this should work (or at least get you something you can work with):
SELECT
b.id, b.maxdate, a.type
FROM
records a -- this is the records table, where you'll get the type
INNER JOIN -- now join it to the group by query
(select id, max(rdate) as maxdate FROM records GROUP BY id) b
ON -- join on both rdate and id, otherwise you'll get lots of duplicates
b.id = a.id
AND b.maxdate = a.rdate
Note that if you have records with different types for the same id and rdate combination you'll get duplicates.
Related
I'm trying to find duplicate rows in a large database (300,000 records). Here's an example of how it looks:
| id | title | thedate |
|----|---------|------------|
| 1 | Title 1 | 2021-01-01 |
| 2 | Title 2 | 2020-12-24 |
| 3 | Title 3 | 2021-02-14 |
| 4 | Title 2 | 2021-05-01 |
| 5 | Title 1 | 2021-01-13 |
I found this excellent (i.e. fast) answer here: Find duplicate rows with PostgreSQL
-- adapted from #MatthewJ answering in https://stackoverflow.com/questions/14471179/find-duplicate-rows-with-postgresql/14471928#14471928
select * from (
SELECT id, title, TO_DATE(thedate,'YYYY-MM-DD'),
ROW_NUMBER() OVER(PARTITION BY title ORDER BY id asc) AS Row
FROM table1
) dups
where
dups.Row > 1
Which I'm trying to use as a base to solve my specific problem: I need to find duplicates according to column values like in the example, but only for records posted within 15 days of each other (the date of record insertion in the column "thedate" in my DB).
I reproduced it in this fiddle http://sqlfiddle.com/#!15/ae109/2, where id 5 (same title as id 1, and posted within 15 days of each other) should be the only acceptable answer.
How would I implement that condition in the query?
With the LAG function you can get the date from the previous row with the same title and then filter based on the time difference.
WITH with_prev AS (
SELECT
*,
LAG(thedate, 1) OVER (PARTITION BY title ORDER BY thedate) AS prev_date
FROM table1
)
SELECT id, title, thedate
FROM with_prev
WHERE thedate::timestamp - prev_date::timestamp < INTERVAL '15 days'
You don't necessarily need window funtions for this, you an use a plain old self-join, like:
select p.id, p.thedate, n.id, n.thedate, p.title
from table1 p
join table1 n on p.title = n.title and p.thedate < n.thedate
where n.thedate::date - p.thedate::date < 15
http://sqlfiddle.com/#!15/a3a73a/7
This has the advantage that it might use some of your indexes on the table, and also, you can decide if you want to use the data (i.e. the ID) of the previous row or the next row from each pair.
If your date column however is not unique, you'll need to be a little more specific in your join condition, like:
select p.id, p.thedate, n.id, n.thedate, p.title
from table1 p
join table1 n on p.title = n.title and p.thedate <= n.thedate and p.id <> n.id
where n.thedate::date - p.thedate::date < 15
In my Postgresql 9.3 database I have a table stock_rotation:
+----+-----------------+---------------------+------------+---------------------+
| id | quantity_change | stock_rotation_type | article_id | date |
+----+-----------------+---------------------+------------+---------------------+
| 1 | 10 | PURCHASE | 1 | 2010-01-01 15:35:01 |
| 2 | -4 | SALE | 1 | 2010-05-06 08:46:02 |
| 3 | 5 | INVENTORY | 1 | 2010-12-20 08:20:35 |
| 4 | 2 | PURCHASE | 1 | 2011-02-05 16:45:50 |
| 5 | -1 | SALE | 1 | 2011-03-01 16:42:53 |
+----+-----------------+---------------------+------------+---------------------+
Types:
SALE has negative quantity_change
PURCHASE has positive quantity_change
INVENTORY resets the actual number in stock to the given value
In this implementation, to get the current value that an article has in stock, you need to sum up all quantity changes since the latest INVENTORY for the specific article (including the inventory value). I do not know why it is implemented this way and unfortunately it would be quite hard to change this now.
My question now is how to do this for more than a single article at once.
My latest attempt was this:
WITH latest_inventory_of_article as (
SELECT MAX(date)
FROM stock_rotation
WHERE stock_rotation_type = 'INVENTORY'
)
SELECT a.id, sum(quantity_change)
FROM stock_rotation sr
INNER JOIN article a ON a.id = sr.article_id
WHERE sr.date >= (COALESCE(
(SELECT date FROM latest_inventory_of_article),
'1970-01-01'
))
GROUP BY a.id
But the date for the latest stock_rotation of type INVENTORY can be different for every article.
I was trying to avoid looping over multiple article ids to find this date.
In this case I would use a different internal query to get the max inventory per article. You are effectively using stock_rotation twice but it should work. If it's too big of a table you can try something else:
SELECT sr.article_id, sum(quantity_change)
FROM stock_rotation sr
LEFT JOIN (
SELECT article_id, MAX(date) AS date
FROM stock_rotation
WHERE stock_rotation_type = 'INVENTORY'
GROUP BY article_id) AS latest_inventory
ON latest_inventory.article_id = sr.article_id
WHERE sr.date >= COALESCE(latest_inventory.date, '1970-01-01')
GROUP BY sr.article_id
You can use DISTINCT ON together with ORDER BY to get the latest INVENTORY row for each article_id in the WITH clause.
Then you can join that with the original table to get all later rows and add the values:
WITH latest_inventory as (
SELECT DISTINCT ON (article_id) id, article_id, date
FROM stock_rotation
WHERE stock_rotation_type = 'INVENTORY'
ORDER BY article_id, date DESC
)
SELECT article_id, sum(sr.quantity_change)
FROM stock_rotation sr
JOIN latest_inventory li USING (article_id)
WHERE sr.date >= li.date
GROUP BY article_id;
Here is my take on it: First, build the list of products at their last inventory state, using a window function. Then, join it back to the entire list, filtering on operations later than the inventory date for the item.
with initial_inventory as
(
select article_id, date, quantity_change from
(select article_id, date, quantity_change, rank() over (partition by article_id order by date desc)
from stockRotation
where type = 'INVENTORY'
) a
where rank = 1
)
select ii.article_id, ii.quantity_change + sum(sr.quantity_change)
from initial_inventory ii
join stockRotation sr on ii.article_id = sr.article_id and sr.date > ii.date
group by ii.article_id, ii.quantity_change
I have two tables Employee and Dept as below
EIN | ENAME | Salary | DeptID
1 | Ravi | 500 | 10
2 | Krishna | 1000 | 20
3 | Kiran | 1500 | 20
DeptID | DeptName
10 | IT
20 | Finance
I want the output as employees along with Deptname who is getting maximum salary group by dept
Here is an option which does not use analytic functions:
SELECT e.ENAME,
COALESCE(d.DeptName, 'NA') AS DeptName,
t.max_salary
FROM Employee e
LEFT JOIN Dept d
ON e.DeptID = d.DeptID
INNER JOIN
(
SELECT DeptID, MAX(SALARY) AS max_salary
FROM Employee
GROUP BY DeptId
) t
ON e.DeptID = t.DeptID AND
e.Salary = t.max_salary
Note that in the event that more than one employee should have the maximum salary in a given department, this query would return all ties. In the absence of further information, this seems reasonable without being able to distinguish one employee from another.
Update:
You could also use a WHERE clause containing a correlated subquery instead of joining to a (non-correlated) subquery as I gave above. Here is what that would look like:
SELECT e.ENAME,
COALESCE(d.DeptName, 'NA') AS DeptName,
e.Salary
FROM Employee e
LEFT JOIN Dept d
ON e.DeptID = d.DeptID
WHERE e.Salary = (SELECT MAX(t.Salary) FROM Employee t WHERE t.DeptID = e.DeptID)
However, I would recommend using the first option as it would probably perform better than the correlated subquery option.
I have a single table laid out as such:
id | name | count
1 | John |
2 | Jim |
3 | John |
4 | Tim |
I need to fill out the count column such that the result is the number of times the specific name shows up in the column name.
The result should be:
id | name | count
1 | John | 2
2 | Jim | 1
3 | John | 2
4 | Tim | 1
I can get the count of occurrences of unique names easily using:
SELECT COUNT(name)
FROM table
GROUP BY name
But that doesn't fit into an UPDATE statement due to it returning multiple rows.
I can also get it narrowed down to a single row by doing this:
SELECT COUNT(name)
FROM table
WHERE name = 'John'
GROUP BY name
But that doesn't allow me to fill out the entire column, just the 'John' rows.
you can do that with a common table expression:
with counted as (
select name, count(*) as name_count
from the_table
group by name
)
update the_table
set "count" = c.name_count
from counted c
where c.name = the_table.name;
Another (slower) option would be to use a co-related sub-query:
update the_table
set "count" = (select count(*)
from the_table t2
where t2.name = the_table.name);
But in general it is a bad idea to store values that can easily be calculated on the fly:
select id,
name,
count(*) over (partition by name) as name_count
from the_table;
Another method : Using a derived table
UPDATE tb
SET count = t.count
FROM (
SELECT count(NAME)
,NAME
FROM tb
GROUP BY 2
) t
WHERE t.NAME = tb.NAME
Please see http://sqlfiddle.com/#!6/9254d/3/0
I have two tables, Person and Values, PersonID is the link between them. Each person in the Values table has multiple values per day for every hour. I need to get the latest value for each user. I had a look on SO and what I could find was to get MAX(ValueDate) and then join on that but doesn't work. Join on PersonID didn't work either, not sure what else to try.
The output I need is
Name Value
1fn 1ln 2
2fn 2ln 20
3fn 3ln 200
I don't need the greatest value, I need the latest value for each person. Please share if you have any ideas. Thanks.
Try this:
SQLFIDDLEExample
DECLARE #Org nvarchar(3)
SELECT #Org = 'aaa'
DECLARE #MyDate date
SELECT #MyDate = CONVERT(date, '2014-09-12')
SELECT a.Name,
a.Value as Revenue
FROM(
SELECT p.FName + ' ' + p.LName AS Name,
vt.Value,
ROW_NUMBER()OVER(PARTITION BY vt.PersonID ORDER BY vt.ValueDate desc) as rnk
FROM Person p
LEFT JOIN ValueTable vt
ON vt.PersonID = p.PersonID
WHERE vt.ValueDate < DATEADD(day,1,#MyDate)
AND vt.ValueDate >= #MyDate
AND vt.Org = #Org)a
WHERE a.rnk = 1
ORDER BY a.Name ASC
Result:
| NAME | REVENUE |
|---------|---------|
| 1fn 1ln | 2 |
| 2fn 2ln | 20 |
| 3fn 3ln | 200 |