I have the following query that works fine
SELECT RecordID, ROW_NUMBER() OVER (ORDER BY (Value1) DESC) AS Rank
FROM Table1
Also, I have another table(table2) that contains (among others) the fields RecordID and Rank. I would like to update RecordID and Rank in table2 based on result of query above. Is that possible?
Yes, you can have multiple tables in an update in Postgres:
update table2
set rank = t1.rank
from (SELECT RecordID, ROW_NUMBER() OVER (ORDER BY (Value1) DESC) AS Rank
FROM Table1
) t1
where table2.RecordId = t1.RecordId;
What worked for me (in mysql) was :
update table2, (SELECT RecordID, ROW_NUMBER() OVER (ORDER BY (Value1) DESC) AS Rank
FROM Table1) tempTable
set table2.Rank = tempTable.Rank
where table2.RecordId = tempTable.RecordId;
Related
Wondering if it is possible to creating a new column and filter on that column. The following is an example:
SELECT row_number() over (partition by ID order by date asc) row# FROM table1 where row# = 1
Thanks!
Some databases support a QUALIFY clause which you might be able to use:
SELECT *
FROM table1
QUALIFY ROW_NUMBER() OVER (PARTITION BY ID ORDER BY date) = 1;
On SQL Server, you may use a TOP 1 WITH TIES trick:
SELECT TOP 1 WITH TIES *
FROM table1
ORDER BY ROW_NUMBER() OVER (PARTITION BY ID ORDER BY date);
More generally, you would have to use a subquery:
WITH cte AS (
SELECT t.*, ROW_NUMBER() OVER (PARTITION BY ID ORDER BY date) rn
FROM table1 t
)
SELECT *
FROM cte
WHERE rn = 1;
The WHERE clause is evaluated before the SELECT so your column has to exist before you can use a WHERE clause. You could achieve this by making a subquery of the original query.
SELECT *
FROM
(
SELECT row_number() over (partition by ID order by date asc) row#
FROM table1
) a
WHERE a.row# = 1
I have one table. From that I need to get latest "Date" for each "id". I wrote query for One id. But I don't know how to apply for multiple ids.(I mean for each id)
My query for one id is (say table name is tt):
select * from (
SELECT DISTINCT id ,date FROM tt
WHERE Trim(id) ='1000082'
ORDER BY date desc
) where rownum<=1;
If you have just two columns, aggregation is good enough:
select id, max(date) max_date
from mytable
group by id
If you have more columns and you want the entire row that has the latest date for each id, then one option uses a correlated subquery for filtering:
select t.*
from mytable t
where t.date = (select max(t1.date) from mytable t1 where t1.id = t.id)
Or you can use window functions, if your database supports them:
select *
from (select t.*, row_number() over(partition by id order by date desc) rn from mytable t) t
where rn = 1
I have a quite large table with a field ID and another field as collection_time. I want to select latest record for each ID. Unfortunately combination of (ID, collection_time) time is not unique together in my data. I want just one of records with the maximum collection time. I have tried two solutions but none of them has worked for me:
First: using query
SELECT * FROM
(SELECT *, ROW_NUMBER() OVER (PARTITION BY ID ORDER BY collection_time) as rn
FROM mytable) where rn=1
This results in Resources exceeded error that I guess is because of ORDER BY in the query.
Second
Using join between table and latest time:
(SELECT tab1.*
FROM mytable AS tab1
INNER JOIN EACH
(SELECT ID, MAX(collection_time) AS second_time
FROM mytable GROUP EACH BY ID) AS tab2
ON tab1.ID=tab2.ID AND tab1.collection_time=tab2.second_time)
this solution does not work for me because (ID, collection_time) are not unique together so in JOIN result there would be multiple rows for each ID.
I am wondering if there is a workaround for the resourcesExceeded error, or a different query that would work in my case?
SELECT
agg.table.*
FROM (
SELECT
id,
ARRAY_AGG(STRUCT(table)
ORDER BY
collection_time DESC)[SAFE_OFFSET(0)] agg
FROM
`dataset.table` table
GROUP BY
id)
This will do the job for you and is scalable considering the fact that the schema keeps changing, you won't have to change this
Short and scalable version:
select array_agg(t order by collection_time desc limit 1)[offset(0)].*
from mytable t
group by t.id;
Quick and dirty option - combine your both queries into one - first get all records with latest collection_time (using your second query) and then dedup them using your first query:
SELECT * FROM (
SELECT *, ROW_NUMBER() OVER (PARTITION BY tab1.ID) AS rn
FROM (
SELECT tab1.*
FROM mytable AS tab1
INNER JOIN (
SELECT ID, MAX(collection_time) AS second_time
FROM mytable GROUP BY ID
) AS tab2
ON tab1.ID=tab2.ID AND tab1.collection_time=tab2.second_time
)
)
WHERE rn = 1
And with Standard SQL (proposed by S.Mohsen sh)
WITH myTable AS (
SELECT 1 AS ID, 1 AS collection_time
),
tab1 AS (
SELECT ID,
MAX(collection_time) AS second_time
FROM myTable GROUP BY ID
),
tab2 AS (
SELECT * FROM myTable
),
joint AS (
SELECT tab2.*
FROM tab2 INNER JOIN tab1
ON tab2.ID=tab1.ID AND tab2.collection_time=tab1.second_time
)
SELECT * EXCEPT(rn)
FROM (
SELECT *, ROW_NUMBER() OVER (PARTITION BY ID) AS rn
FROM joint
)
WHERE rn=1
If you don't care about writing a piece of code for every column:
SELECT ID,
ARRAY_AGG(col1 ORDER BY collection_time DESC)[OFFSET(0)] AS col1,
ARRAY_AGG(col2 ORDER BY collection_time DESC)[OFFSET(0)] AS col2
FROM myTable
GROUP BY ID
I see no one has mentioned window functions with QUALIFY:
SELECT *, MAX(collection_time) OVER (PARTITION BY id) AS max_timestamp
FROM my_table
QUALIFY collection_time = max_timestamp
The window function adds a column max_timestamp that is accessible in the QUALIFY clause to filter on.
As per your comment, Considering you have a table with unique ID's for which you need to find latest collection_time. Here is another way to do it using Correlated Sub-Query. Give it a try.
SELECT id,
(SELECT Max(collection_time)
FROM mytable B
WHERE A.id = B.id) AS Max_collection_time
FROM id_table A
Another solution, which could be more scalable since it avoids multiple scans of the same table (which will happen with both self-join and correlated subquery in above answers). This solution only works with standard SQL (uncheck "Use Legacy SQL" option):
SELECT
ID,
(SELECT srow.*
FROM UNNEST(t.srows) srow
WHERE srow.collection_time = MAX(srow.collection_time))
FROM
(SELECT ID, ARRAY_AGG(STRUCT(col1, col2, col3, ...)) srows
FROM id_table
GROUP BY ID) t
What I am trying to accomplish:
Dataset 1
Name1
Name2
Name3
Dataset 2
Number1
Number2
Number3
will become 2 columns:
dataset1 dataset2
Name1 Number1
Name2 Number2
Name3 Number3
My datasets 1 & 2 will always have equal rows.
Which name linked to which number I don't care as long as two names are not linked to the same number and vice versa.
How can I solve this with SQL / SQL Server ?
If you don't want to add an identity column to the tables, you can use the ROW_NUMBER() function like this:
SELECT
T1.Col1,
T2.Col1
FROM
(SELECT Col1, ROW_NUMBER() OVER (ORDER BY Col1) AS N FROM Table1) T1
INNER JOIN
(SELECT Col1, ROW_NUMBER() OVER (ORDER BY Col1) AS N FROM Table2) T2
ON T1.N = T2.N
Here, replace Table1 and Table2 with the name of your tables, and replace Col1 with the name of the column (or columns) that you want to output from the two tables.
Add identity columns to both the tables and perform join on basis of these column
ALTER TABLE Table1
ADD ID INT IDENTITY(1,1) NOT NULL
ALTER TABLE Table2
ADD ID INT IDENTITY(1,1) NOT NULL
SELECT Table1.dataset1col , Table2.dataset2Col
From Table1 INNER JOIN Table2
ON Table1.ID = Table2.ID
This may work for you :
;WITH cte1 (name, rn)
AS (SELECT Name,
row_number()
OVER(
ORDER BY Name) rn
FROM Dataset1),
cte2 (Number, rn)
AS (SELECT Number,
row_number()
OVER(
ORDER BY Number) rn
FROM Dataset2)
SELECT name,
Number
FROM cte1
JOIN cte2
ON cte1.rn = cte2.rn
WITH Table1 AS
(
SELECT ROW_NUMBER() OVER (PARTITION BY ID ORDER BY Dataset1) as Rnk,Dataset1
FROM TA1
)
With Table2 AS
(
SELECT ROW_NUMBER() OVER (PARTITION BY ID ORDER BY Dataset2) as Rnk, Dataset2
FROM TA2
)
Select Table.Dataset1 as 'DataSet1', Table2.DataSet2 as 'DataSet2'
From Table1
inner join Table2 on Table1.Rnk = Table2.Rnk
Because you haven't added table name so I considered it as TA1 and TA2.
Another way of writing the query is:
select row_number() over (order by Names asc) as rownum,
Names
into #Temp1
from NameTable
select row_number() over (order by Numbers asc) as rownum,
Numbers
into #Temp2
from NumberTable
select Names, Numbers
from #Temp1
inner join #Temp2 on #Temp1.rownum = #Temp2.rownum
Demo
There are 3 possible solutions to this.
First: Use following trick (Warning: Use this in case of small datasets)
SELECT DISTINCT tbl1.col1, tbl2.col2
FROM
(SELECT FirstName AS col1, ROW_NUMBER() OVER (ORDER BY FirstName) Number FROM dbo.User) tbl1
INNER JOIN
(SELECT LastName AS col2, ROW_NUMBER() OVER (ORDER BY LastName) Number FROM dbo.User) tbl2
ON tbl1.Number = tbl2.Number
Second: Use variable tables to store result temporarily. This solution is for relatively large datasets. (approx records to 100s)
Third:
Use identitfy field in both tables as already mentioned by mmhasannn. But i will prefer this method least, as we need to modify our DB structure.
RECOMMENDED: Use variable tables approach
Hi I'm kinda new to mssql, I'm used to Oracle. I'm trying to delete a specific row from a subquery but mssql doens't really like subqueries.
Here is the query:
DELETE FROM (SELECT *, ROW_NUMBER() OVER (PARTITION BY column1 ORDER BY column1) row FROM randomtable) a
WHERE a.row = 1
Is there a way to get this to work?
In Oracle I could've get everything in a query because I can use rownum = 1.
You were nearly there
DELETE a
FROM (SELECT *,
ROW_NUMBER() OVER (PARTITION BY column1 ORDER BY column1) row
FROM randomtable) a
WHERE a.row = 1
Though I prefer the CTE syntax
WITH a
AS (SELECT *,
ROW_NUMBER() OVER (PARTITION BY column1 ORDER BY column1) row
FROM randomtable)
DELETE FROM a
WHERE a.row = 1
You didn't specify the table alias in what you wanted to delete from.
DELETE a FROM (SELECT *, ROW_NUMBER() OVER (PARTITION BY column1 ORDER BY column1) row FROM randomtable) a
WHERE a.row = 1
Write the alias DELETE a FROM ...