I have a table and it's data looks like this:
id name date
--------- --------- ----------
1 a 2012-08-30 10:36:27.393
1 b 2012-08-30 14:36:27.393
2 c 2012-08-30 13:36:27.393
2 d 2012-08-30 16:36:27.393
I retrieve the max datetime with this query:
SELECT id,Max(date) as mymaxdate
FROM table1
group by id
This query givse me two rows like this:
1 2012-08-30 14:36:27.393
2 2012-08-30 16:36:27.393
It's correct, but how can i change it to retrieve this result?
1 b 2012-08-30 14:36:27.393
2 d 2012-08-30 16:36:27.393
Thanks
For SQL Server 2005+
WITH cteMaxDate AS (
SELECT id, name, date,
ROW_NUMBER() OVER(PARTITION BY id ORDER BY date DESC) AS RowNum
FROM table1
)
SELECT id, name, date
FROM cteMaxDate
WHERE RowNum = 1;
One of the options:
select
t1.id
,t1.name
,t1.date
from
table1 t1
inner join (
SELECT id,Max(date) as mymaxdate
FROM table1
group by id
) mt1
on t1.id = mt1.id
and t1.date = mt1.mymaxdate
Related
I need the below select results to be converted into single row ,
Actual output:
ORDER POSTCODE Quantity Value
123456 AAAAA 22.78 5
123456 AAAAA 2.93 7
Expected Output:
ORDER POSTCODE AmbientQuantity Ambientvalue FVQuantity FvVAlue
123456 AAAAA 22.78 5 2.93 7
How to achieve the expected output in db2?
Following SQL will do the job:
with temp as (
select ORDER, POSTCODE, QUANTITY, VALUE,
rownumber() over (partition by ORDER, POSTCODE) as rownum
FROM mytable2
)
select ORDER, POSTCODE,
max(case when rownum = 1 Then QUANTITY end) as AMBIENTQUANTITY,
max(case when rownum = 1 Then VALUE end) as AMBIENTVALUE,
max(case when rownum = 2 Then QUANTITY end) as FVQuantity,
max(case when rownum = 2 Then VALUE end) as FVVALUE
from temp
group by ORDER, POSTCODE
Try something like this:
with tmp as (
select f0.*, rownumber() over(partition by f0.ORDER, f0.POSTCODE) rang
from your table f0
)
select
f1.ORDER, f1.POSTCODE, f1.Quantity AmbientQuantity, f1.Value Ambientvalue,
f2.Quantity FVQuantity2, f2.Value FvVAlue2,
f3.Quantity FVQuantity3, f2.Value FvVAlue3,
f4.Quantity FVQuantity4, f2.Value FvVAlue4
from tmp f1
left outer join tmp f2 on (f1.ORDER, f1.POSTCODE)=(f2.ORDER, f2.POSTCODE) and f2.rang=2
left outer join tmp f3 on (f1.ORDER, f1.POSTCODE)=(f3.ORDER, f3.POSTCODE) and f3.rang=3
left outer join tmp f4 on (f1.ORDER, f1.POSTCODE)=(f4.ORDER, f4.POSTCODE) and f4.rang=4
where f1.rang=1
I have 2 tables
students:
id | name | age
1 abc 20
2 xyz 21
scores:
id | studentid | marks
1 1 20
2 2 22
3 2 20
4 1 22
5 1 20
where studentid is foreign key to students table
When a do
select studentid
from scores
where marks=20;
I get the following result
1, 2, 1
But if want the name of the student name and when I do a join using
select t1.name
from students t1
inner join scores t2 on t1.id = t2.studentid
where t2.marks=20;
I get xyz,abc,abc Though the ouput is correct is there any way I can maintain the order in which scores are listed in the scores table? I should get abc,xyz,abc as output. I tried using subquery as well
SELECT name
FROM students
WHERE ID IN ( select studentid from scores where marks=20) ;
but that also did not give me correct order. How can this be achieved using CTEs (common table expressions)? I tried the follownig cte but it did not work
with cte as(
select t2.id, t1.name
from students t1
inner join scores t2 on t1.id = t2.studentid
where t2.marks=20)
select name from cte order by id
You can order by a column not present in select list:
select t1.name
from students t1
inner join scores t2 on t1.id = t2.student_id
where t2.marks=20
order by t2.id;
name
------
abc
xyz
abc
(3 rows)
For an example, I would like to select id with max date group by category, the result is: 7, 2, 6
id category date
1 a 2013-01-01
2 b 2013-01-03
3 c 2013-01-02
4 a 2013-01-02
5 b 2013-01-02
6 c 2013-01-03
7 a 2013-01-03
8 b 2013-01-01
9 c 2013-01-01
This is the SQL I think can work:
SELECT * FROM Table1 t1
JOIN
(
SELECT category, MAX(date) AS MAXDATE
FROM Table1
GROUP BY category
) t2
ON T1.category = t2.category
AND t1.date = t2.MAXDATE
But how to translate that into a query on Ecto?
You can use subquery function
subquery = from t in "Table1"
|> select([t], %{categoty: t.category, max_date: max(t.date)})
|> group_by([t], t.category)
from t in "Table1"
|> join(:inner, [u], t in subquery(subquery), t.category == u.category and t.max_date == u.date)
|> Repo.all
An issue with many frameworks is that they cannot capture all the complexities of a SQL SELECT statement. The easiest solution: wrap your complex query in a view:
CREATE VIEW my_complex_view AS
SELECT * FROM Table1 t1
JOIN (
SELECT category, MAX(date) AS maxdate
FROM Table1
GROUP BY category) t2
ON t1.category = t2.category AND t1.date = t2.maxdate;
Now you have a simple query (SELECT * FROM my_complex_view) which any decent framework can easily handle.
I have a table and it's data looks like this:
id name date
--------- --------- ----------
1 a 2012-08-30 10:36:27.393
1 b 2012-08-30 14:36:27.393
2 c 2012-08-30 13:36:27.393
2 d 2012-08-30 16:36:27.393
I retrieve the max date time with this query:
select
t1.id
,t1.name
,t1.date
from
table1 t1
inner join (
SELECT id,Max(date) as mymaxdate
FROM table1
group by id
) mt1
on t1.id = mt1.id
and t1.date = mt1.mymaxdate
result:
1 b 2012-08-30 14:36:27.393
2 d 2012-08-30 16:36:27.393
how can write this query in entity?
Thanks
The tricky part is that you also want the name of the item having the max date, otherwise the grouping would be much simpler. But it is possible by an almost 1:1 reproduction of the sql query:
from t in table1
join m in
(from t in table1
group t by t.id into g
select new { g.Key, mymaxdate = g.Max (x => x.date) })
on new { t.id, t.date } equals new { id = m.Key, date = m.mymaxdate }
select t
A join on multiple fields is done by creating anonymous types (new {t.id, t.date} and new {id = m.Key, date = m.mymaxdate}) where the names and types of the properties (id and date) should match.
My table is like
ID FName LName Date(mm/dd/yy) Sequence Value
101 A B 1/10/2010 1 10
101 A B 1/10/2010 2 20
101 X Y 1/2/2010 1 15
101 Z X 1/3/2010 5 10
102 A B 1/10/2010 2 10
102 X Y 1/2/2010 1 15
102 Z X 1/3/2010 5 10
I need a query that should return 2 records
101 A B 1/10/2010 2 20
102 A B 1/10/2010 2 10
that is max of date and max of sequence group by id.
Could anyone assist on this.
-----------------------
-- get me my rows...
-----------------------
select * from myTable t
-----------------------
-- limiting them...
-----------------------
inner join
----------------------------------
-- ...by joining to a subselection
----------------------------------
(select m.id, m.date, max(m.sequence) as max_seq from myTable m inner join
----------------------------------------------------
-- first group on id and date to get max-date-per-id
----------------------------------------------------
(select id, max(date) as date from myTable group by id) y
on m.id = y.id and m.date = y.date
group by id) x
on t.id = x.id
and t.sequence = x.max_seq
Would be a simple solution, which does not take account of ties, nor of rows where sequence is NULL.
EDIT: I've added an extra group to first select max-date-per-id, and then join on this to get max-sequence-per-max-date-per-id before joining to the main table to get all columns.
I have considered your table name as employee..
check the below thing helped you.
select * from employee emp1
join (select Id, max(Date) as dat, max(sequence) as seq from employee group by id) emp2
on emp1.id = emp2.id and emp1.sequence = emp2.seq and emp1.date = emp2.dat
I'm a fan of using the WITH clause in SELECT statements to organize the different steps. I find that it makes the code easier to read.
WITH max_date(max_date)
AS (
SELECT MAX(Date)
FROM my_table
),
max_seq(max_seq)
AS (
SELECT MAX(Sequence)
FROM my_table
WHERE Date = (SELECT md.max_date FROM max_date md)
)
SELECT *
FROM my_table
WHERE Date = (SELECT md.max_date FROM max_date md)
AND Sequence = (SELECT ms.max_seq FROM max_seq ms);
You should be able to optimize this further as needed.