I have a complicated SQL question.
Can we update a column within a SELECT query? Example:
Consider this table:
|ID |SeenAt |
----------------
|1 |20 |
|1 |21 |
|1 |22 |
|2 |70 |
|2 |80 |
I want a SELECT Query that gives for each ID when was it seen for the first time. And when did it seen 'again':
|ID |Start |End |
---------------------
|1 |20 |21 |
|1 |20 |22 |
|1 |20 |22 |
|2 |70 |80 |
|2 |70 |80 |
First, both columns Start and End would have the same value, but when a second row with the same ID is seen we need to update its predecessor to give End the new SeenAt value.
I succeeded to create the Start column, I give the minimum SeenAt value per ID to all IDs. But I can't find a way to update the End column everytime.
Don't mind the doubles, I have other columns that change in every new row
Also, I am working in Impala but I can use Oracle.
I hope that I have been clear enough. Thank you
You could use lead() and nvl():
select id, min(seenat) over (partition by id) seen_start,
nvl(lead(seenat) over (partition by id order by seenat), seenat) seen_end
from t
demo
Start is easy just the MIN of the GROUP
End you need to find the MIN after the SeenAt and in case you don't find it then the current SeenAt
SQL DEMO
SELECT "ID",
(SELECT MIN("SeenAt")
FROM Table1 t2
WHERE t1."ID" = t2."ID") as "Start",
COALESCE(
(SELECT MIN("SeenAt")
FROM Table1 t2
WHERE t1."ID" = t2."ID"
AND t1."SeenAt" < t2."SeenAt")
, t1."SeenAt"
) as End
FROM Table1 t1
OUTPUT
| ID | START | END |
|----|-------|-----|
| 1 | 20 | 21 |
| 1 | 20 | 22 |
| 1 | 20 | 22 |
| 2 | 70 | 80 |
| 2 | 70 | 80 |
you seem to need min() analytic function with a self-join:
select distinct t1.ID,
min(t1.SeenAt) over (partition by t1.ID order by t1.ID) as "Start",
t2.SeenAt as "End"
from tab t1
join tab t2 on t1.ID=t2.ID and t1.SeenAt<=t2.SeenAt
order by t2.SeenAt;
Demo
Related
I have 3 tables in database:
Table 1: violation
| violation_id | violation_name |
|:-------------:|:--------------:|
|1 | No Parking |
|2 | Speed Contest |
|3 | No Helmet |
Table 2: violators
| violator_id | violation_id |
|:-------------:|:--------------:|
|1 |1 |
|2 |1 |
|3 |3 |
Table 2: previous_violator
| prev_violator_id| violation_id |
|:---------------:|:--------------:|
|1 |1 |
|2 |2 |
|3 |2 |
This view that I want:
| violation_name | Total |
|:-------------:|:--------------:|
|No Parking | 3 |
|Speed Contest | 2 |
|No Helmet | 1 |
I perform this code that joins the violator table and violation:
SELECT *,count(violators.violation_id) as vid
FROM violators
LEFT JOIN violation ON violation.violation_id = violators.violation_id
LEFT JOIN previous_violator ON previous_violator.violator_id = violators.violator_id
WHERE date_apphrehend BETWEEN '$from' AND '$to'
GROUP BY violators.violation_id
My problem is, I want to join the previous violator table that count to the total based on the violation_name.
You can first union all to get them into a single result and then count(*) it. Finally join with Violation to get names. ie:
select violation_name, count(*) as cnt
from (select violation_id from Violators
union all
select violation_id from previous_Violators) tmp
inner join Violation on tmp.violation_id = Violation.violation_id
group by Violation.violation_id, violation_name;
Sample DBFiddle demo.
PS: Sample is in postgreSQL but it would be the same for most backends. You didn't tag your backend.
I have several tables
table1
-------------------------
|id| rec | other_rec|
-------------------------
|1 | record1 | record6 |
|2 | record2 | record8 |
|3 | record4 | record0 |
|4 | record5 | record2 |
|n | ... | ... |
------------------------
and a second table
table2
-------------------------------------------------
|id| table_nr_1_foreign_key | rec_1 | rec_2 |
-------------------------------------------------
|1 | table_nr_1_key_1 |record1 | rt1 |
|2 | table_nr_1_key_2 |record2 | rt2 |
|3 | table_nr_1_key_2 |record4 | rt3 |
|4 | table_nr_1_key_3 |record5 | rt4 |
|5 | table_nr_1_key_2 |record6 | rt5 |
|n | table_nr_1_key_n | ... | ... |
-------------------------------------------------
and an SQL query
SELECT t.id,
t.rec,
t.other_rec,
t2.rec_1
FROM table1 t1
JOIN ...[other table]
and ...[conditions start]
and ...
and ...[conditions end]
LEFT JOIN table2 t2 ON t.id = table_nr_1_foreign_key
AND t2.rec_2 = any(array['rt2'])
where ...[other condition]
now I want to select all records from table2 which have a corresponding foreign key in a table1
if and only if at least one record exists in a table2 that points to a table1.
so I want
data1,..., rt2
data1,..., rt3
data1,..., rt5
...
to be selected
but all I get is
data1,..., rt2
Update no 1.
with my inexperience I failed to accomplish selection with one sql and wrote two sql queries instead
for data selection for a main record (table 1)
the other for selecting all records from a table 2 (using in([list
of ids]))
This question can be closed / deleted.
I have two tables:
Operations (op_id,super,name,last)
Orders (or_id,number)
Operations:
+--------------------------------+
|op_id| super| name | last|
+--------------------------------+
|1 1 OperationXX 1 |
|2 1 OperationXY 2 |
|3 1 OperationXC 4 |
|4 1 OperationXZ 3 |
|5 2 OperationXX 1 |
|6 3 OperationXY 2 |
|7 4 OperationXC 1 |
|8 4 OperationXZ 2 |
+--------------------------------+
Orders:
+--------------+
|or_id | number|
+--------------+
|1 2UY |
|2 23X |
|3 xx2 |
|4 121 |
+--------------+
I need query to get table:
+-------------------------------------+
|or_id |number |max(last)| name |
|1 2UY 4 OperationXC|
|2 23X 1 OperationXX|
|3 xx2 2 OperationXY|
|4 121 2 OperationXZ|
+-------------------------------------+
use corelared subquery and join
select o.*,a.last,a.name from
(
select super,name,last from Operations from operations t
where last = (select max(last) from operations t2 where t2.super=t.super)
) a join orders o on t1.super =o.or_id
you can use row_number as well
with cte as
(
select * from
(
select * , row_number() over(partition by super order by last desc) rn
from operations
) tt where rn=1
) select o.*,cte.last,cte.name from Orders o join cte on o.or_id=cte.super
SELECT Orders.or_id, Orders.number, Operations.name, Operations.last AS max
FROM Orders
INNER JOIN Operations on Operations.super = Orders.or_id
GROUP BY Orders.or_id, Orders.number, Operations.name;
I don't have a way of testing this right now, but I think this is it.
Also, you didn't specify the foreign key, so the join might be wrong.
Here's my data
|vendorname |total|
---------------------
|Najla |10 |
|Disney |20 |
|Disney |10 |
|ToysRus |5 |
|ToysRus |1 |
|Gap |1 |
|Gap |2 |
|Gap |3 |
|Najla |2 |
Here's the resultset I want
|vendorname |grandtotal|
---------------------
|Disney |30 |
|Gap |6 |
|ToysRus |6 |
|Najla |2 |
|Najla |10 |
If the vendorname = 'Najla' I want individual rows with their respective total otherwise I would like to group them and return a sum of their totals.
This is my query--
select *
from
(
select vendorname, sum(total) grandtotal
from vendor
where vendorname<>'Najla'
group by vendorname
union all
select vendorname, total grandtotal
from vendor
where vendorname='Najla'
) A
I was wondering if there's a better way to write this query instead of repeating it twice and performing a union. Is there a condensed way to group some rows "conditionally".
Honestly, I think the union all version is going to be the best performing and easiest to read option if it has appropriate indexes.
You could, however, do something like this (assuming you have a unique id on your table):
select vendorname, sum(total) grandtotal
from t
group by
vendorname
, case when vendorname = 'Najla' then id else null end
rextester demo: http://rextester.com/OGZQ33364
returns
+------------+------------+
| vendorname | grandtotal |
+------------+------------+
| Disney | 30 |
| Gap | 6 |
| ToysRus | 6 |
| Najla | 10 |
| Najla | 2 |
+------------+------------+
Table w:
|ID|Comment|SeqID|
|1 |bajg | 1 |
|1 |2423 | 2 |
|2 |ref | 1 |
|2 |comment| 2 |
|2 |juk | 3 |
|3 |efef | 1 |
|4 | hy | 1 |
|4 | 6u | 2 |
How do I insert a standard new comment for each ID for a new SeqID (SeqID increase by 1)
The Below query results in the highest SeqID:
Select *
From w
Where SEQID =
(select max(seqid)
from w)
Table w:
|2 |juk | 3 |
Expected Result
Table w:
|ID|Comment|SeqID|
|1 |sqc | 3 |
|2 |sqc | 4 |
|3 |sqc | 2 |
|4 |sqc | 3 |
Will I have to go through and insert all the values (new comment as sqc) I want into the table using the below, or is there a faster way?
INSERT INTO table_name
VALUES (value1,value2,value3,...);
Try this:
INSERT INTO mytable (ID, Comment, SeqID)
SELECT ID, 'sqc', MAX(SeqID) + 1
FROM mytable
GROUP BY ID
Demo here
You are probably better off just calculating the value when you query. Define an identity column on the table, say CommentId and run a query like:
select id, comment,
row_number() over (partition by comment order by CommentId) as SeqId
from t;
What is nice about this approach is that the ids are always sequential, you don't have no opportunities for duplicates, the table does not have to be locked to when inserting, and the sequential ids work even for updates and deletes.