Suppose I have a table called spitems with the following fields:
spitemid (unique key)
modifiedon (timestamp)
parentid
a number of other unsignificant fields
What I want to retrieve, is the spitem rows with the highest modifiedon day for each parentid.
However, be aware that the modifiedon timestamp is not unique, so it is possible that for one parent id, there are two spitemids with the same modifiedon timestamp. In that case, I need one of these two spitemids listed, I don't care which one.
So to be clear: the list I return should contain all the parentids once and only once.
update
meeting over, here is my shot:
select *
from table
join where spitmid in
(select max(spitmid)
from table
join
(select parentid, max(modifiedon) as d from table group by parentid) inlist
on table.parentid = inlist.parentid and table.modifiedon = inlist.d
group by parentid, datemodified
)
old entry
not sure if this is different on DB2, here it is for sql server.
select *
from table
join (select parentid, max(modifiedon) as d from table group by parentid) as toplist on
table.parentid = toplist.parentid and table.modifiedon = toplist.d
hmm... this will return more than one for the dups... can't fix it now, have to go to a meeting.
Based on your requirements, following should get you the latest items.
SELECT t1.*
FROM Table t1
INNER JOIN (
SELECT spitemid = MAX(t1.spitemid)
FROM Table t1
INNER JOIN (
SELECT parentid, modifiedon = MAX(modifiedon)
FROM Table
GROUP BY parentid
) t2 ON t2.parentid = t1.parentid
AND t2.modifiedon = t1.modifiedon
GROUP BY t1.parentid, t1.modifiedon
) t2 ON t2.spitemid = t1.spitemid
You can do it with two nested subqueries. The first gets max modifiedon for each parentid, and then the second gets max spitemid for each parentid/modifiedon group.
SELECT *
FROM spitems
WHERE spitemid IN
(
SELECT parentid, modifiedon, max(spitemid) spitemid
FROM (
SELECT parentid, MAX(modifiedon) modifiedon
FROM spitems
GROUP BY parentid
) A
GROUP BY parentid, modifiedon
)
A common table expression will give you the opportunity to number the rows before you issue the final SELECT.
WITH items AS
(
SELECT spitemid, parentid, modifiedon,
ROWNUMBER() OVER (PARTITION BY parentid ORDER BY modifiedon DESC) AS rnum
FROM yourTable
)
SELECT spitemid, parentid, modifiedon FROM items WHERE rnum = 1
;
SELECT sr.receiving_id, sc.collection_id FROM stock_collection as sc, stock_requisation as srq, stock_receiving as sr WHERE (sc.stock_id = '" & strStockID & "' AND sc.datemm_issued = '" & strMM & "' AND sc.qty_issued >= 0 AND sc.collection_id = srq.requisition_id AND srq.active_status = 'Active') OR (sr.stock_id = '" & strStockID & "' AND sr.datemm_received = '" & strMM & "' AND sr.qty_received >= 0)
Related
Name Value AnotherColumn
-----------
Pump 1 8000.0 Something1
Pump 1 10000.0 Something2
Pump 1 10000.0 Something3
Pump 2 3043 Something4
Pump 2 4594 Something5
Pump 2 6165 Something6
My table looks something like this. I would like to know how to select max value for each pump.
select a.name, value from out_pumptable as a,
(select name, max(value) as value from out_pumptable where group by posnumber)g where and g.value = value
this code does the job, but i get two entries of Pump 1 since it has two entries with same value.
select name, max(value)
from out_pumptable
group by name
select name, value
from( select name, value, ROW_NUMBER() OVER(PARTITION BY name ORDER BY value desc) as rn
from out_pumptable ) as a
where rn = 1
SELECT
b.name,
MAX(b.value) as MaxValue,
MAX(b.Anothercolumn) as AnotherColumn
FROM out_pumptabl
INNER JOIN (SELECT
name,
MAX(value) as MaxValue
FROM out_pumptabl
GROUP BY Name) a ON
a.name = b.name AND a.maxValue = b.value
GROUP BY b.Name
Note this would be far easier if you had a primary key. Here is an Example
SELECT * FROM out_pumptabl c
WHERE PK in
(SELECT
MAX(PK) as MaxPK
FROM out_pumptabl b
INNER JOIN (SELECT
name,
MAX(value) as MaxValue
FROM out_pumptabl
GROUP BY Name) a ON
a.name = b.name AND a.maxValue = b.value)
select Name, Value, AnotherColumn
from out_pumptable
where Value =
(
select Max(Value)
from out_pumptable as f where f.Name=out_pumptable.Name
)
group by Name, Value, AnotherColumn
Try like this, It works.
select * from (select * from table order by value desc limit 999999999) v group by v.name
Using analytic function is the easy way to find max value of every group.
Documentation : https://learn.microsoft.com/en-us/sql/t-sql/functions/row-number-transact-sql?view=sql-server-ver15
Select name,
value,
AnotherColumn
From(
SELECT Row_Number() over(partition by name order by value desc)as
row_number, *
FROM students
)
Where row_number = 1
SELECT t1.name, t1.Value, t1.AnotherColumn
FROM mytable t1
JOIN (SELECT name AS nameMax, MAX(Value) as valueMax
FROM mytable
GROUP BY name) AS t2
ON t2.nameMax = t1.name AND t2.valueMax = t1.Value
WHERE 1 OR <anything you would like>
GROUP BY t1.name;
SELECT DISTINCT (t1.ProdId), t1.Quantity FROM Dummy t1 INNER JOIN
(SELECT ProdId, MAX(Quantity) as MaxQuantity FROM Dummy GROUP BY ProdId) t2
ON t1.ProdId = t2.ProdId
AND t1.Quantity = t2.MaxQuantity
ORDER BY t1.ProdId
this will give you the idea.
Given a table of timestamp,user_id,country,site_id.
How do you find the number of users whose first/last visits are the same website?
/* unique users first site*/
SELECT ts,SWE.site_id, SWE.user_id
FROM SWE
WHERE SWE.ts = (
SELECT MIN(t.timestamp)
FROM SWE t
WHERE
t.user_id = SWE.user_id
)
/* unique users last site*/
SELECT ts,SWE.site_id, SWE.user_id
FROM SWE
WHERE SWE.ts = (
SELECT max(t.timestamp)
FROM SWE t
WHERE
t.user_id = SWE.user_id
)
I am not sure how to count when these are equal?
I'd use the DISTINCT ON operator to pick out the first/last visits for each user, then aggregate over these to check if they're different. something like:
WITH first_visits AS (
SELECT DISTINCT ON (user_id) * FROM user_visits
ORDER BY user_id, timestamp
), last_visits AS (
SELECT DISTINCT ON (user_id) * FROM user_visits
ORDER BY user_id, timestamp DESC
)
SELECT user_id,
array_to_string(array_agg(DISTINCT site_id), ', ') AS sites,
MIN(timestamp) AS first_visit, MAX(timestamp) as last_visit
FROM (
SELECT * FROM first_visits
UNION ALL
SELECT * FROM last_visits) x
GROUP BY user_id
HAVING COUNT(DISTINCT site_id) = 1;
I have this table:
CREATE TABLE items (
id SERIAL PRIMARY KEY,
data TEXT,
parent INT,
posted INT
);
Each item has a piece of data, a timestamp, and a parent. I'd like to select the top 10 root items (parent = 0), sorted by the timestamp of the most recent child.
If item #1 has a child #2 that has a child #3, #3 is considered a child of #1.
How can I do this?
EDIT:
The query has been rewritten to
first sort the child items
get the root parent id and the rank for each item
select the top 10 parents
select the details for the top 10 parents
Common Table expressions have been used to incrementally select the data following the above steps.
WITH recursive c AS
(
SELECT *
FROM seeds
UNION ALL
SELECT
T.id,
T.parent,
c.topParentID,
(c.child_level + 1),
c.child_rank
FROM items AS T
INNER JOIN c ON T.parent = c.id
WHERE T.id <> T.parent
)
, seeds AS
(
SELECT
id,
parent,
parent AS topParentID,
0 AS child_level,
rank() OVER (ORDER BY posted DESC) child_rank
FROM items
WHERE parent <> 0
ORDER BY posted DESC
)
, rank_level AS
(
SELECT DISTINCT
c2.id id,
c_ranks.min_child_rank child_rank,
c_roots.max_child_level root_level
FROM
(
SELECT
id,
MAX(child_level) max_child_level
FROM c
GROUP BY id
)
c_roots
INNER JOIN c c2 ON c_roots.id = c2.id
INNER JOIN
(
SELECT
id,
MIN(child_rank) min_child_rank
FROM c
GROUP BY id
)
c_ranks
ON c2.id = c_ranks.id
)
, top_10_parents AS
(
SELECT
c.topParentID id,
MIN(rl.child_rank) id_rank
FROM rank_level rl
INNER JOIN c ON rl.id = c.id AND c.child_level = rl.root_level
GROUP BY c.topParentID
ORDER BY MIN(rl.child_rank)
limit 10
)
SELECT
i.*
FROM
items i
INNER JOIN top_10_parents tp ON tp.id = i.id
ORDER BY tp.id_rank;
SQL Fiddle
Reference:
WITH Queries (Common Table Expressions) on PostgreSQL Manual
I'm using MS-SQL 2012
WITH C1
(
SELECT ID, 0 as Match, Field2, Count(*)
FROM TableX
GROUP BY ID, Fields2
)
UPDATE C1 SET Match = 1
WHERE ID = (SELECT MATCHING_ID FROM AnotherTable WHERE ID = C1.ID)
This TSQL statement gives me the following error:
Update or insert of view or function 'C1' failed because it contains a derived or constant field.
Ideally I would like to create a "fake field" named Match and set its default value to 0. Then with the update I would like to Update ONLY the records that have an existing entry on the "AnotherTable".
Any thoughts what am I doing wrong?
Thanks in advanced.
Try doing a Left Outer Join like
SELECT x.ID, ISNULL(a.Matching_ID, 0) as Match, x.Field2, Count(*)
FROM TableX x
LEFT OUTER JOIN AnotherTable a on x.ID = a.ID
GROUP BY x.ID, ISNULL(a.Matching_ID, 0), x.Fields2
without the need of a C1
If I am understanding correctly, the problem is that you are trying to update the CTE table. If you update the table directly you should be fine.
Does this modified version help?
SELECT t.ID
, CASE WHEN (EXISTS (SELECT MATCHING_ID FROM AnotherTable WHERE ID = t.ID)) THEN 1 ELSE 0 END
,t.Field2
,Count(*)
FROM TableX t
GROUP BY ID, Fields2
Can you let me know how to select only two employees from every department? The table has deptname, ssn, name . I am doing a sampling and I need only two ssns for every department name. Can someone help?
You can accomplish this with an "OLAP expression" row_number()
with e as
( select deptname, ssn, empname,
row_number() over (partition by dptname order by empname) as pick
from employees
)
select deptname, ssn, empname
from e
where pick < 3
order by deptname, ssn
This example will give you the two employees with the lowest order names, because that is what is specified in the row_number() (order by) expression.
Try this:
select *
from t t1
where (
select count(*)
from t t2
where
t2.deptname = t1.deptname
and
t2.ssn <= t1.ssn) <= 2
order by deptname, ssn,name;
The above will give "smallest" two ssn.
If you want top 2, change to t2.ssn >= t1.ssn
sqlfiddle
The data:
The result from query:
select * from
( select rank() over (partition by dptname order by empname) as count , *
from employees
)
where count<=2
order by deptname, ssn,name;