I am new to SQL and I am no good with more advanced queries and functions.
So, I have this 1 table with sales:
id date seller_name buyer_name
---- ------------ ------------- ------------
1 2015-02-02 null Adrian
1 2013-05-02 null John B
1 2007-11-15 null Chris F
2 2014-07-12 null Jane A
2 2011-06-05 null Ted D
2 2010-08-22 null Maryanne A
3 2015-12-02 null Don P
3 2012-11-07 null Chris T
3 2011-10-02 null James O
I would like to update the seller_name for each id, by putting the buyer_name from previous sale as seller_name to newer sale date. For example, for on id 1 John B would then be seller in 2015-02-02 and buyer in 2013-05-02. Does that make sense?
P.S. This is the perfect case, the table is big and the ids are not ordered so neat.
merge into your_table a
using ( select rowid rid,
lead(buyer_name, 1) over (partition by id order by date desc) seller
from your_table
) b
on (a.rowid = b.rid )
when matched then update set a.seller_name= b.seller;
Explanation : Merge into statement performs different operations based on matched or not matched criterias. Here you have to merge into your table, in the using having the new values that you want to take and also the rowid which will be your matching key. The lead function gets the result from the next n rows depending on what number you specify after the comma. After specifying how many rows to jump you also specify on what part to work, which in your case is partitioned by id and ordered by date so you can get the seller, who was the previous buyer. Hope this clears it up a bit.
Either of the below query can be used to perform the desire action
merge into sandeep24nov16_2 table1
using(select rowid r, lag(buyer_name) over (partition by id order by "DATE" asc) update_value from sandeep24nov16_2 ) table2
on (table1.rowid=table2.r)
when matched then update set table1.seller_name=table2.update_value;
or
merge into sandeep24nov16_2 table1
using(select rowid r, lead(buyer_name) over (partition by id order by "DATE" desc) update_value from sandeep24nov16_2 ) table2
on (table1.rowid=table2.r)
when matched then update set table1.seller_name=table2.update_value;
select a.*,
lag(buyer_name, 1) over(partition by id order by sale_date) seller_name
from <your_table> a;
Related
i have a table called "main" which has 4 columns, ID, name, DateID and Sign.
i want to create a query that will delete entries in this table if there is the same ID record in twice within a certain DateID.
i have my where clause that searches the previous 3 weeks
where DateID =((SELECT MAX( DateID)
WHERE DateID < ( SELECT MAX( DateID )-3))
e.g of my dataset im working with:
id
name
DateID
sign
12345
Paul
1915
Up
23658
Danny
1915
Down
37868
Jake
1916
Up
37542
Elle
1917
Up
12345
Paul
1917
Down
87456
John
1918
Up
78563
Luke
1919
Up
23658
Danny
1920
Up
in the case above, both entries for ID 12345 would need to be removed.
however the entries for ID 23658 would need to be kept as the DateID > 3
how would this be possible?
You can use window functions for this.
It's not quite clear, but it seems LAG and conditional COUNT should fit what you need.
DELETE t
FROM (
SELECT *,
CountWithinDate = COUNT(CASE WHEN t.PrevDate >= t.DateId - 3 THEN 1 END) OVER (PARTITION BY t.id)
FROM (
SELECT *,
PrevDate = LAG(t.DateID) OVER (PARTITION BY t.id ORDER BY t.DateID)
FROM YourTable t
) t
) t
WHERE CountWithinDate > 0;
db<>fiddle
Note that you do not need to re-join the table, you can delete directly from the t derived table.
Hope this works:
DELETE FROM test_tbl
WHERE id IN (
SELECT T1.id
FROM test_tbl T1
WHERE EXISTS (SELECT 1 FROM test_tbl T2 WHERE T1.id = T2.id AND ABS(T2.dateid - T1.dateid) < 3 AND T1.dateid <> T2.dateid)
)
In case you need more logic for data processing, I would suggest using Stored Procedure.
How can I delete rows where dateupdated was least updated ?
My table is
Name Dateupdated ID status
john 1/02/17 JHN1 A
john 1/03/17 JHN2 A
sally 1/02/17 SLLY1 A
sally 1/03/17 SLLY2 A
Mike 1/03/17 MK1 A
Mike 1/04/17 MK2 A
I want to be left with the following after the data removal:
Name Date ID status
john 1/03/17 JHN2 A
sally 1/03/17 SLLY2 A
Mike 1/04/17 MK2 A
If you really want to "delete rows where dateupdated was least updated" then a simple single-row subquery should do the trick.
DELETE MyTable
WHERE Date = (SELECT MIN(Date) From MyTable)
If on the other hand you just want to delete the row with the earliest Date per person (as identified by their ID) you could use:
DELETE MyTable
FROM MyTable a
JOIN (SELECT ID, MIN(Date) MinDate FROM MyTable GROUP BY ID) b
ON a.ID = b.ID AND a.Date = b.MinDate
The idea here is you create an aggregate query that returns rows containing the columns that would match the rows you want deleted, then join to it. Because it's an inner join, rows that do not match the criteria will be excluded.
If people are uniquely identified by something else (e.g. Name then you can just substitute that for the ID in my example above.
I am thinking though that you don't want either of these. I think you want to delete everything except for each person's latest row. If that is the case, try this:
DELETE MyTable
WHERE EXISTS (SELECT 0 FROM MyTable b WHERE b.ID = MyTable.ID AND b.Date > MyTable.Date)
The idea here is you check for existence of another data row with the same ID and a later date. If there is a later record, delete this one.
The nice thing about the last example is you can run it over and over and every person will still be left with exactly one row. The other two queries, if run over and over, will nibble away at the table until it is empty.
P.S. As these are significantly different solutions, I suggest you spend some effort learning how to articulate unambiguous requirements. This is an extremely important skill for any developer.
This deletes rows where the name is a duplicate, and deletes all but the latest row for each name. This is different from your stated question.
Using a common table expression (cte) and row_number():
;with cte as (
select *
, rn = row_number() over (
partition by Name
order by Dateupdated desc
)
from t
)
/* ------------------------------------------------
-- Remove duplicates by deleting rows
-- where the row number (rn) is greater than 1
-- leaving the first row for each partition
------------------------------------------------ */
delete
from cte
where cte.rn > 1
select * from t
rextester: http://rextester.com/HZBQ50469
returns:
+-------+-------------+-------+--------+
| Name | Dateupdated | ID | status |
+-------+-------------+-------+--------+
| john | 2017-01-03 | JHN2 | A |
| sally | 2017-01-03 | SLLY2 | A |
| Mike | 2017-01-04 | MK2 | A |
+-------+-------------+-------+--------+
Without using the cte it can be written as:
delete d
from (
select *
, rn = row_number() over (
partition by Name
order by Dateupdated desc
)
from t
) as d
where d.rn > 1
This should do the trick:
delete
from MyTable a
where not exists (
select top 1 1
from MyTable b
where b.name = a.name
and b.DateUpdated < a.DateUpdated
)
i.e. remove any entries from the table for which there is no record on the same name with a date earlier than the record to be deleted's.
Your Name column has Mike and Mik2 which is different for each other.
So, if you did not make a mistake, standard column to group by must be ID column without last digit.
I think following is more accurate if you did not mistaken.
delete a
from MyTable a
inner join
(select substring(ID, 1, len(ID) - 1) as ID, min(Dateupdated) as MinDate
from MyTable
group by substring(ID, 1, len(ID) - 1)
) b
on substring(a.ID, 1, len(a.ID) - 1) = b.ID and a.Dateupdated = b.MinDate
You can test it at SQLFiddle: http://sqlfiddle.com/#!6/9c440/1
Lets say I have a table like this:
id | peru | usa
1 20 10
2 5 100
3 1 5
How can I get the top values from peru and usa as well as the spefic ids. So that I get as result:
usa_id: 2 | usa: 100 | peru_id: 1 | peru: 20
Is this possible In one query? Or do I have to do two ORDER BY querys?
Im using postgresql
You can do this with some subqueries and a cross join:
select
u.id usa_id,
u.usa,
p.id peru_id,
p.peru
from
(select id, usa from mytable where usa=(select max(usa) from mytable) order by id limit 1) u
cross join (select id, peru from mytable where peru=(select max(peru) from mytable) order by id limit 1) p
;
In the case that there are multiple rows with the same max value (for usa or peru, independently), this solution will select the one with the lowest id (I've assumed that id is unique).
SELECT
t1.id as peru_id, t1.peru
, t2.id as usa_id, t2.usa
FROM tab1 t1, tab1 t2
ORDER BY t1.peru desc, t2.usa desc
limit 1
http://sqlfiddle.com/#!15/0c12f/6
As basicly what this does is a simple carthesian product - I guess that performance WILL be poor for large datasets.
on the fiddle it took 196ms for a 1k rows table. On 10k rows table - sqlFiddle hung up.
You can consider using MAX aggregate function in conjunction with ARRAY type. Check this out:
CREATE TEMPORARY TABLE _test(
id integer primary key,
peru integer not null,
usa integer not null
);
INSERT INTO _test(id, peru, usa)
VALUES
(1,20,10),
(2,5,100),
(3,1,5);
SELECT MAX(ARRAY[peru, id]) AS max_peru, MAX(array[usa, id]) AS max_usa FROM _test;
SELECT x.max_peru[1] AS peru, x.max_peru[2] AS peru_id, x.max_usa[1]
AS usa, x.max_usa[2] AS usa_id FROM (
SELECT MAX(array[peru, id]) AS max_peru,
MAX(array[usa, id]) AS max_usa FROM _test ) as x;
I'm attempting to perform a GROUP BY on a join table table. The join table essentially looks like:
CREATE TABLE user_foos (
id SERIAL PRIMARY KEY,
user_id INT NOT NULL,
foo_id INT NOT NULL,
effective_at DATETIME NOT NULL
);
ALTER TABLE user_foos
ADD CONSTRAINT user_foos_uniqueness
UNIQUE (user_id, foo_id, effective_at);
I'd like to query this table to find all records where the effective_at is the max value for any pair of user_id, foo_id given. I've tried the following:
SELECT "user_foos"."id",
"user_foos"."user_id",
"user_foos"."foo_id",
max("user_foos"."effective_at")
FROM "user_foos"
GROUP BY "user_foos"."user_id", "user_foos"."foo_id";
Unfortunately, this results in the error:
column "user_foos.id" must appear in the GROUP BY clause or be used in an aggregate function
I understand that the problem relates to "id" not being used in an aggregate function and that the DB doesn't know what to do if it finds multiple records with differing ID's, but I know this could never happen due to my trinary primary key across those columns (user_id, foo_id, and effective_at).
To work around this, I also tried a number of other variants such as using the first_value window function on the id:
SELECT first_value("user_foos"."id"),
"user_foos"."user_id",
"user_foos"."foo_id",
max("user_foos"."effective_at")
FROM "user_foos"
GROUP BY "user_foos"."user_id", "user_foos"."foo_id";
and:
SELECT first_value("user_foos"."id")
FROM "user_foos"
GROUP BY "user_foos"."user_id", "user_foos"."foo_id"
HAVING "user_foos"."effective_at" = max("user_foos"."effective_at")
Unfortunately, these both result in a different error:
window function call requires an OVER clause
Ideally, my goal is to fetch ALL matching id's so that I can use it in a subquery to fetch the legitimate full row data from this table for matching records. Can anyone provide insight on how I can get this working?
Postgres has a very nice feature called distinct on, which can be used in this case:
SELECT DISTINCT ON (uf."user_id", uf."foo_id") uf.*
FROM "user_foos" uf
ORDER BY uf."user_id", uf."foo_id", uf."effective_at" DESC;
It returns the first row in a group, based on the values in parentheses. The order by clause needs to include these values as well as a third column for determining which is the first row in the group.
Try:
SELECT *
FROM (
SELECT t.*,
row_number() OVER( partition by user_id, foo_id ORDER BY effective_at DESC ) x
FROM user_foos t
)
WHERE x = 1
If you don't want to use a sub query based on a composite of all three keys then you need to create a "dense rank" window function field that orders subsets of id, user_id and foo_id by effective date with the rank order field. Then subquery that and take the records where rank_order=1. Since the rank ordering was by effective date you are getting all fields of the record with the highest effective date for each foo and user.
DATSET
1 1 1 01/01/2001
2 1 1 01/01/2002
3 1 1 01/01/2003
4 1 2 01/01/2001
5 2 1 01/01/2001
DATSET WITH RANK ORDER PARTITIONED BY FOO_ID, USER_ID ORDERED BY DATE DESC
1 3 1 1 01/01/2001
2 2 1 1 01/01/2002
3 1 1 1 01/01/2003
4 1 1 2 01/01/2001
5 1 2 1 01/01/2001
SELECT * FROM QUERY ABOVE WHERE RANK_ORDER=1
3 1 1 1 01/01/2003
4 1 1 2 01/01/2001
5 1 2 1 01/01/2001
I have a table containing the below column
person_id Person_Name Telephone_No City Email_Id Insert_TS
and there are certain other column like Alternate_name etc.
In this table, whenever there is any update in any of the particular a row is inserted . For example
P01 Radhe 0112311231 Bia b#b.com 09-NOV-2012 15:24:38
P01 Radhe Null Bia a#b.com 30-APR-2014 21:26:51
P02 Shayam 456897845 Albi s#b.com 30-APR-2014 14:36:03
P03 Radha Null xyz s1#b.com 31-APR-2014 14:36:03
Means, few record contains null in telephone field but all other fields have data
I want to display person_id Person_Name Telephone_No City Email_Id columns such that if there is any row containing telephone_no value not null corresponding to one person_id then the latest record of that should be displayed
else
latest record of the person should be displayed
to summarize display unique person_id with latest telephone_no for those person which does not have telephone_no latest record should be displayed.
I tried this way :
Get the unique person_id with latest telephone_no -- A
Get all unique person_id with latest record --- B
display the data as (B-A) + A .
But that is taking too much time and that does not seems to be efficient .
Please suggest a query to fetch the records faster
Other possible way could be using the case statement on group by result like grouping the values by Person_id if there is any telephone_no in each group display the one with latest value otherwise display the latest entry from group
Would it not be sufficient to always show the last row for each person? Assuming person_id, Insert_TS is unique:
select person_id, max(Insert_TS)
from T
group by person_id
then join that with the table to get all info.
For recent versions of oracle you can use row_number() as in
select ...
from (
select ..., row_number() over (partition by person_id
order by Insert_TS desc) as rn
) as x
where rn = 1;
I'm not sure I fully understand but here's a try. I get errors from SQLFiddle for Oracle, and I don't have access to Oracle my self so the following is tested on DB2 V10.5. I simplified a bit by removing a couple of columns. Furthermore the timestamps are different than yours:
with tmp as (select PERSON_ID, PERSON_NAME, TELEPHONE_NO, INSERT_TS
,row_number() over (partition by person_id
order by insert_ts desc) as rn
from t)
select * from tmp x
where rn = (
select coalesce(min(rn),1)
from tmp y
where x.person_id = y.person_id
and y.TELEPHONE_NO is not null
);
PERSON_ID PERSON_NAME TELEPHONE_NO INSERT_TS RN
--------- ----------- --------------- -------------------------- --------------------
P01 Radhe 011231123109 2012-05-22-14.27.35.037579 2
P02 Shayam 456897845 2014-05-22-14.27.35.037579 1
P03 Radha - 2014-06-22-14.27.35.037579 1
3 record(s) selected.