Let's say I have a Turtle table. When I run
SELECT * FROM Turtle ORDER BY Sort
I get this:
Id | Name | Sort
2 Leo 1
3 Raph 2
4 Don 5
1 Mike 7
What is the easiest way to close the gaps between Raph and Don, and between Don and Mike, so that the table looks like this?
Id | Name | Sort
2 Leo 1
3 Raph 2
4 Don 3
1 Mike 4
This should work no matter how many turtles are in the table, and no matter how many gaps there are or how long each gap is.
You can do the update just using a CTE with the row_number(), and then just update the CTE:
;with CTE as (
select *, row_number () over (order by Sort) as RN
from Turtle
)
update CTE
set Sort = RN
Try this
SELECT ID, Name, ROW_NUMBER() OVER(ORDER BY Sort) AS Sort FROM Turtle
Here's the answer I came up with:
UPDATE t
SET t.Sort = t2.Sort
FROM Turtle AS t,
(SELECT Id, Sort = ROW_NUMBER() OVER(ORDER BY Sort) FROM Turtle) as t2
WHERE t.Id = t2.Id
We can select the Turtle table as t2, ordering the turtles by the Sort column, but assigning the ROW_NUMBER() to the Sort column. We can then use the new value in t2.Sort to update each row in the Turtle table where the Ids match.
Edit (based on Juan Carlos Oropeza's feedback):
Here is the code using an explicit JOIN instead.
UPDATE t
SET t.Sort = t2.Sort
FROM Turtle AS t
JOIN (SELECT Id, ROW_NUMBER() OVER(ORDER BY Sort) AS Sort FROM Turtle) AS t2 ON t.Id = t2.Id
This is what they mean by using a cte in an update.
;WITH cte AS
(
SELECT *, ROW_NUMBER() OVER(ORDER BY Sort) NewSort
FROM Turtle
)
UPDATE cte SET Sort = NewSort
Related
I have a table called body_scan that looks like this:
body_no tag
--------------------
1 noscan
2 noscan
3 missing
4 noscan
5 missing
I also have a list that I can load into a temp table like so
tag_no
------
aaa
bbb
ccc
What I need to be able to do is to update the body_scan table with the tag numbers in the temporary table.
You will notice that there are only 3 tags in the temp table but 5 in the body_scan table. I need to update the tag value "noscan" with values from the temp table and leave the missing as they are..
The order of the tags in the temporary table is the same as the order of body_no from the body_scan table.
So yes, I did consider the row_number() function. But I'm just not 100% sure how to define the join correctly..
How do I achieve this please?
The desired result is :
body_no tag
-------------------
1 aaa
2 bbb
3 missing
4 ccc
5 missing
Firstly, you need to preserve the input file order of data by adding an identity field to the temp_table (note that some ETL tools insert data in parallel and that messes things up so you might even need to add this column to the file)
Once you've done that, you need to generate a key in body_scan that you can join to. This is simply ROW_NUMBER() over the existing table, excluding the missing rows
This returns the row and what it should be matched to in temp_table
SELECT
body_no,
ROW_NUMBER() OVER (ORDER BY body_no) RN
FROM body_scan
WHERE tag<> 'missing';
This joins in the temp table (assumes your ordinal column is called RowID)
SELECT T1.body_no, T1.tag, T1.RN, T2.tag_no
FROM
(
SELECT
body_no,tag,
ROW_NUMBER() OVER (ORDER BY body_no) RN
FROM body_scan
WHERE tag<> 'missing'
) T1
INNER JOIN
temp_table T2
ON T1.RN=T2.RowID;
This updates it back to the table:
UPDATE TGT
SET tag=SRC.tag_no
FROM body_scan TGT
INNER JOIN
(
SELECT T1.body_no, T2.tag_no
FROM
(
SELECT
body_no,tag,
ROW_NUMBER() OVER (ORDER BY body_no) RN
FROM body_scan
WHERE tag<> 'missing'
) T1
INNER JOIN
temp_table T2
ON T1.RN=T2.RowID
) SRC
ON SRC.body_no=TGT.body_no;
(There's half a dozen ways to write that final statement but I prefer this way as you can see the dataset you're updating from in the subselect)
I cant understand your explanation and command discussion. I workout(in SQL 2012) to achieve your OUTPUT table. As,
update a
set a.tag = t.tag
from (
select m.*, ROW_NUMBER() over(partition by m.tag order by m.rn)trn from(
select *, row_number() over(partition by (select null) order by (select null)) rn from body_scan --set order what the order of actual table's order
) m --set row number for noscan rows
) a
join(
select *, ROW_NUMBER() over(order by (select null)) rn from #temp --set order what the order of actual table order
) t
on a.trn = t.rn and a.tag <> 'missing' -- join to noscan rows using row numbers
OUTPUT:
body_no tag
--------------
1 aaa
2 bbb
3 missing
4 ccc
5 missing
I am stuck with this. I have a simple set-up with two tables. One table is holding emailaddresses one table is holding vouchercodes. I want to join them in a third table, so that each emailaddress has one random vouchercode.
Unfortunatly I am stuck with this as there are no identic Ids to match both values. What I have so far brings no result:
Select
A.Email
B.CouponCode
FROM Emailaddresses as A
JOIN CouponCodes as B
on A.Email = B.CouponCode
A hint would be great as search did not bring me any further yet.
Edit -
Table A (Addresses)
-------------------
Column A | Column B
-------------------------
email1#gmail.com True
email2#gmail.com
email3#gmail.com True
email4#gmail.com
Table B (Voucher)
-------------------
ABCD1234
ABCD5678
ABCD9876
ABCD5432
Table C
-------------------------
column A | column B
-------------------------
email1#gmail.com ABCD1234
email2#gmail.com ABCD5678
email3#gmail.com ABCD9876
email4#gmail.com ABCD5432
Sample Data:
While joining without proper keys is not a good solution, for your case you can try this. (note: not tested, just a quick suggestion)
;with cte_email as (
select row_number() over (order by Email) as rownum, Email
from Emailaddresses
)
;with cte_coupon as (
select row_number() over (order by CouponCode) as rownum, CouponCode
from CouponCodes
)
select a.Email,b.CouponCode
from cte_email a
join cte_coupon b
on a.rownum = b.rownum
You want to randomly join records, one email with one coupon each. So create random row numbers and join on these:
select
e.email,
c.couponcode
from (select t.*, row_number() over (order by newid()) as rn from emailaddresses t) e
join (select t.*, row_number() over (order by newid()) as rn from CouponCodes t) c
on c.rn = e.rn;
Give a row number for both the tables and join it with row number.
Query
;with cte as(
select [rn] = row_number() over(
order by [Column_A]
), *
from [Table_A]
),
cte2 as(
select [rn] = row_number() over(
order by [Column_A]
), *
from [Table_B]
)
select t1.[Column_A] as [Email_Id], t2.[Column_A] as [Coupon]
from cte t1
join cte2 t2
on t1.rn = t2.rn;
Find a demo here
I have a table t1 with two int fields(id,month) and I have populated it with some values.
What I would like to see as an output is, the maximum of (count of id in a month). I have tried the following code and it works fine:
select id,max(freq) as maxfreq from
(select id,month,count(*) as freq
from t1
group by id,month) a
group by id
order by maxfreq desc
The result is:
ID MAXFREQ
1 3
2 3
3 1
4 1
This is fine. How to achieve this using the over partition by clause? And which one is more efficient? In reality my table consists of several thousands of records. So doing a subquery wont be a good idea I guess! Thanks for any help. Here's the fiddle
;WITH tmp AS (select id, row_number() over (partition by id, month order by id) rn
FROM t1)
SELECT t.id, max(tmp.rn) as maxfreq
from t1 t
INNER JOIN tmp ON tmp.id = t.id
GROUP BY t.id
You can try this -
select id,max(freq) as maxfreq from
(select id,row_number() over (partition by id,month ORDER BY id) as freq
from t1
) a
group by id
order by id,maxfreq desc
but from a performance standpoint, I do not see much difference between your original query and this one.
Same solution but with using CTE.
Actually there is no point to forcibly use windowing functions to this issue.
Compare both solutions with plan explorer.
;with c1 as
( select id,month,count(*) as freq
from t1
group by id,month
)
select id, max(freq) as maxfreq
from c1
group by id
order by maxfreq desc;
MSSQL
Table looks like so
ID 1 | 2 | 3 | 4 | 5
AA1 1 | 1 | 1 | 2 | 1
any clues on how I could make a query to return
ID | MaxNo
AA1 | 4
, usign the above table example? I know I could write a case blah when statement, but I have a feeling there's a much simpler way of doing this
You can use UNPIVOT to get these comparable items, correctly1, into the same column, and then use ROW_NUMBER() to find the highest valued row2:
declare #t table (ID char(3) not null,[1] int not null,[2] int not null,
[3] int not null,[4] int not null,[5] int not null)
insert into #t (ID,[1],[2],[3],[4],[5]) values
('AA1',1,1,1,2,1)
;With Unpivoted as (
select *,ROW_NUMBER() OVER (ORDER BY Value desc) rn
from #t t UNPIVOT (Value FOR Col in ([1],[2],[3],[4],[5])) u
)
select * from Unpivoted where rn = 1
Result:
ID Value Col rn
---- ----------- ------------------------- --------------------
AA1 2 4 1
1 If you have data from the same "domain" appearing in multiple columns in the same table (such that it even makes sense to compare such values), it's usually a sign of attribute splitting, where part of your data has, incorrectly, been used to form part of a column name.
2 In your question, you say "per row", and yet you've only given a one row sample. If we assume that ID values are unique for each row, and you want to find the maximum separately for each ID, you'd write the ROW_NUMBER() as ROW_NUMBER() OVER (PARTITION BY ID ORDER BY Value desc) rn, to get (I hope) the result you're looking for.
You can use a cross apply where you do max() over the columns for one row.
select T1.ID,
T2.Value
from YourTable as T1
cross apply
(
select max(T.Value) as Value
from (values (T1.[1]),
(T1.[2]),
(T1.[3]),
(T1.[4]),
(T1.[5])) as T(Value)
) as T2
If you are on SQL Server 2005 you can use union all in the derived table instead of values().
select T1.ID,
T2.Value
from YourTable as T1
cross apply
(
select max(T.Value) as Value
from (select T1.[1] union all
select T1.[2] union all
select T1.[3] union all
select T1.[4] union all
select T1.[5]) as T(Value)
) as T2
SQL Fiddle
I was trying to select the second last row with SQL Server. So I wrote a query like this:
SELECT TOP 1 * From Cinema
WHERE CinemaID!=(SELECT TOP 1 CinemaID
FROM Cinema
ORDER BY CinemaID DESC)
ORDER BY CinemaID DESC
and it did what I need. But I want to do the same thing with only one select.
I read that the LIMIT clause in MySql does that. But I couldn't find any equivalent
of that. So I appreciate any help about finding something useful.
To get the 2nd last row in one select:
SELECT TOP 1 * From
(select Top 2 * from Cinema ORDER BY CinemaID DESC) x
ORDER BY CinemaID
It's really only "one" select because the outer select is over only 2 rows.
The best way to do this (and compatible with the ANSI SQL standard), is to use a CTE (Common Table Expression) with the ROW_NUMBER function:
;WITH OrderedCinemas AS
(
SELECT
CinemaID, CinemaName,
ROW_NUMBER() OVER(ORDER BY CinemaID DESC) AS 'RowNum'
FROM dbo.Cinema
)
SELECT
CinemaID, CinemaName
FROM OrderedCinemas
WHERE RowNum = 2
By using this construction, you can get the second highest value very easily - or the fifth hightest (WHERE RowNum = 5) or the top 3 rows (WHERE RowNum <= 3) or whatever you need - the CinemaID values are just ordered and sequentially numbered for your use.
The following doesn't work, explaination of why:
Using ranking-function derived column in where clause (SQL Server 2008)
I'll keep it here for completeness:
SELECT row_number() OVER (ORDER BY col) r, *
FROM tbl
WHERE r = 2
More info:
http://www.bidn.com/blogs/marcoadf/bidn-blog/379/ranking-functions-row_number-vs-rank-vs-dense_rank-vs-ntile
So I think the most readable way of doing it is:
SELECT * FROM (SELECT row_number() OVER (ORDER BY col) r, * FROM tbl) q
WHERE r = 2
Since this (old) question has not been tagged with a specific SQL-Server version and none of (the very good) answers uses only one SELECT clause - for the good reason that it was not possible in old verions - here is one that works only in recent, 2012+ versions:
SELECT c.*
FROM dbo.Cinema AS c
ORDER BY CinemaID DESC
OFFSET 1 ROW
FETCH FIRST 1 ROW ONLY ;
Tested at SQLFiddle
SELECT TOP 1 * FROM tbl_CompanyMaster
where Companyid >= (SELECT MAX(Companyid) - 1 FROM tbl_CompanyMaster)
select * from TABLE_NAME order by COLUMN_NAME desc limit 1,1 ;
Where COLUMN_NAME should be "primary key" or "Unique"
Two selects but a bit quicker
select top 1 * from(
SELECT TOP 2 * From Cinema
WHERE CinemaID
ORDER BY CinemaID DESC) top2
Order by CinemaID
So, in the spirit of only using one SELECT clause as stated in the OP and thoroughly abusing T-SQL in general, I proffer something I would never, ever recommend using in production that nevertheless satisfies the stated criteria:
update Cinema
set Cinema.SomeField = Cinema.SomeField
output inserted.*
from Cinema
inner join
(
select top 2 CinemaID, ROW_NUMBER() over (order by CinemaID desc) as RowNum
from Cinema
) rsRowNum on rsRowNum.CinemaID = Cinema.CinemaID
where RowNum = 2
This query will also work for SQLITE
SELECT * From
(select * from Cinema ORDER BY CinemaID DESC LIMIT 2) AS name
ORDER BY CinemaID LIMIT 1
You're only using one SELECT statement. A SELECT statement can include an arbitrary (more or less) number of subqueries--correlated subqueries, scalar subqueries, and so on, each with their own SELECT clause. But it's still just one SELECT statement.
If you want to avoid a subquery, you could select the top 2, and skip the one you don't want. That kind of programming is pretty brittle, though. You have to remember what to skip every time; sooner or later, you'll forget.
SELECT field_name FROM (SELECT TOP 2 field_name FROM table_name
ORDER BY field_name DESC)
WHERE rownum = 2;
select top 1* from(SELECT TOP 2 * From Cinema
WHERE CinemaID
ORDER BY CinemaID DESC) XYZ
ORDER BY CinemaID
where XYZ is not a keyword. It is just a word. And word can be anything.
If you need to do that, but:
the column is different than id
you need to order by some specific column
can't use SELECT on FROM clause (if you are using old versions of Hibernate, per example).
You can do:
select top 1 * from Cinema
where date < (select MAX(date) from Cinema)
order by date desc
The easiest way to get second last row from sql table is user ORDER BY CinemaID DESC and set LIMIT 1,1
TRY THIS
SELECT * from `Cinema` ORDER BY `CinemaID` DESC LIMIT 1,1
select * from
(select ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) as R, * from Cinema ) T1
where (select count(*) from Cinema ) - T1.R = 1
SELECT * FROM record
WHERE record_id=(SELECT max(record_id)-1 FROM record)
Here is my code:
SELECT * From
(select * from table name ORDER BY column name DESC LIMIT 2) AS xyz
ORDER BY column name LIMIT 1;