I have an oracle database with a table containing data that may start with the same prefix and would like to find rows that the 5 digit prefix is duplicated somewhere in the table.
For Example:
Table1
---------------
12345-brsd
12345-wbgb
12345-ydad
34573-diwe
75234-daie
72456-woei
72456-wdgq
I want to return only the ones that the first 5 digits are duplicate, so out of this sample:
12345-brsd
12345-wbgb
12345-ydad
72456-woei
72456-wdgq
You can do this using analytic functions:
select t.*
from (select t.*, count(*) over (partition by substr(column, 1, 5)) as cnt
from table t
) t
where cnt > 1
order by column1;
Related
I have a table that looks something like this when ORDERED by R_Value Desc
Note that it is important to understand that the below table is SQL SELECT ordered by R_Value
Id Letter R_Value
1 A 1500
2 A 1400
4 B 800
9 B 700
10 B 600
11 A 400
12 A 200
I want my result set to look like this. The result set needs to be grouped 3
times. Each time, the letter changes from A to B or vice versa, a new group should
be formed.
Letter Max_RValue
A 1500
B 800
A 400
I have already experimented with various things- lead/lag functions, partitioning, etc. and it seems impossible. A simple Group by(Letter) obviously won't work because
all 'A' will be put in one group which is not what I want.
My next step would be to try this in a procedural language, dump it in an
intermediate table and then read the results. Before doing that, is this even
possible in Ordinary SQL?
You can use LAG() window function to check the previous value of Letter for each row and SUM() window function to create the groups of rows of consecutive occurrences.
Then aggregate in each group:
SELECT Letter, MAX(R_Value) Max_RValue
FROM (
SELECT *, SUM(flag::int) OVER (ORDER BY R_Value DESC) grp
FROM (
SELECT *, Letter <> LAG(Letter, 1, '') OVER (ORDER BY R_Value DESC) flag
FROM tablename
) t
) t
GROUP BY grp, Letter;
Or, simpler just select the rows where the Letter changes:
SELECT Letter, R_Value
FROM (
SELECT *, LAG(Letter, 1, '') OVER (ORDER BY R_Value DESC) prev_Letter
FROM tablename
) t
WHERE Letter <> prev_Letter;
See the demo.
Forpas's second solution is okay but it can be written more simply in Postgres as:
select letter, r_value
from (select t.*, lag(letter) over (order by r_value) as prev_letter
from t
) t
where prev_letter is distinct from letter;
New to SQL here - I am trying to get 1 row from a table matching to a particular criteria
Typically this would look like
SELECT TOP 1 *
FROM myTable
WHERE id = 'abc'
The output may look like
value id
--------------
1 abc
The table has many entries for an 'id', and I am trying to get one entry per 'id'. Now I have list of 'id's. How would I execute something like
SELECT TOP 1 *
FROM myTable
FOR EACH id
WHERE id IN ('abc', 'edf', 'fgh')
Expecting result like
value id
--------------
1 abc
10 edf
12 fgh
I do not know if it is some sort union or concat operation, but would like to learn. I am working on Azure SQL Server
The table has many entries for an 'id', and I am trying to get one entry per 'id'. Now I have list of 'id's.
A typical method is row_number():
select t.*
from (select t.*,
row_number() over (partition by id order by id) as seqnum
from mytable t
) t
where seqnum = 1;
Note: you can filter on particular ids, if you want. It is unclear if that is really required for your question.
If you happen to be using SQL Server (as select top suggests), you can use the more concise, but somewhat less performant:
select top (1) with ties t.*
from mytable t
order by row_number() over (order by id order by (select null));
I have a table that look like this:
The problem is I need to get the last record with duplicates in the column "NRODENUNCIA".
You can use MAX(DENUNCIAID), along with GROUP BY... HAVING to find the duplicates and select the row with the largest DENUNCIAID:
SELECT MAX(DENUNCIAID), NRODENUNCIA, FECHAEMISION, ADUANA, MES, NOMBREESTADO
FROM YourTable
GROUP BY NRODENUNCIA, FECHAEMISION, ADUANA, MES, NOMBREESTADO
HAVING COUNT(1) > 1
This will only show rows that have at least one duplicate. If you want to see non-duplicate rows too, just remove the HAVING COUNT(1) > 1
There are a number of solutions for your problem. One is to use row_number.
Note that I've ordered by DENUNCIID in the OVER clause. This defines the "Last Record" as the one that has the largest DENUNCIID. If you want to define it differently you'd need to change the field that is being ordered.
with dupes as (
SELECT
ROW_NUMBER() OVER (Partition by NRODENUNCIA ORDER BY DENUNCIID DESC) RN,
*
FROM
YourTable
)
SELECT * FROM dupes where rn = 1
This only get's the last record per dupe.
If you want to only include records that have dupes then you change the where clause to
WHERE rn =1
and NRODENUNCIA in (select NRODENUNCIA from dupes where rn > 1)
I am writing a very simple query for an Oracle DB (version 9).
Somehow I can get first 5 rows:
select * from cities where rownum <= 5
But skipping 5 rows returns an empty result:
select * from cities where rownum >= 5
Using:
Oracle SQL Developer
Oracle DB version 9
Why is the second query returning an empty result?
In Oracle Database 12c (release 1) and above, you can do this very simple, for skip 5 rows:
SELECT * FROM T OFFSET 5 ROWS
and for skip 5 rows and take 15 rows:
SELECT * FROM T OFFSET 5 ROWS FETCH NEXT 15 ROWS ONLY
You can use the following query to skip the first not n of rows.
select * from (
select rslts.*, rownum as rec_no from (
<<Query with proper order by (If you don't have proper order by you will see weird results)>>
) rslts
) where rec_no > <<startRowNum - n>>
The above query is similar to pagination query below.
select * from (
select rslts.*, rownum as rec_no from (
<<Query with proper order by (If you don't have proper order by you will see weird results)>>
) rslts where rownum <= <<endRowNum>>
) where rec_no > <<startRowNum>>
Your cities query:
select * from (
select rslts.*, rownum as rec_no from (
select * from cities order by 1
) rslts
) where rec_no > 5 <<startRowNum>>
Note: Assume first column in cities table is unique key
Oracle increments rownum each time it adds a row to the result set. So saying rownum < 5 is fine; as it adds each of the first 5 rows it increments rownum, but then once ruwnum = 5 the WHERE clause stops matching, no more rows are added to the result, and though you don't notice this rownum stops incrementing.
But if you say WHERE rownum > 5 then right off the bat, the WHERE clause doesn't match; and since, say, the first row isn't added to the result set, rownum isn't incremented... so rownum can never reach a value greater than 5 and the WHERE clause can never match.
To get the result you want, you can use row_number() over() in a subquery, like
select *
from (select row_number() over() rn, -- other values
from table
where -- ...)
where rn > 5
Update - As noted by others, this kind of query only makes sense if you can
control the order of the row numbering, so you should really use row_number() over(order bysomething) where something is a useful ordering key in deciding which records are "the first 5 records".
rownum is being increased only when a row is being output, so this type of condition won't work.
In any case, you are not ordering your rows, so what's the point?
Used row_number() over (order by id):
select * from
(select row_number() over (order by id) rn, c.* from countries c)
where rn > 5
Used ROWNUM:
select * from
(select rownum rn, c.* from countries c)
where rn > 5
Important note:
Using alias as countries c instead of countries is required! Without, it gives an error "missing expression"
Even better would be:
select * from mytab sample(5) fetch next 1 rows only;
Sample clause indicates the probability of each row getting picked up in the sampling process. FETCH NEXT clause indicates the number of rows you want to select.
With this code, you can query your table with skip and take.
select * from (
select a.*, rownum rnum from (
select * from cities
) a
) WHERE rnum >= :skip + 1 AND rnum <= :skip + :take
This code works with Oracle 11g. With Oracle 12, there is already a better way to perform this queries with offset and fetch
I'm using SQL Server 2008.
I have a table with x amount of rows. I would like to always divide x by 5 and select the 3rd group of records.
Let's say there are 100 records in the table:
100 / 5 = 20
the 3rd segment will be record 41 to 60.
How will I be able in SQL to calculate and select this 3rd segment only?
Thanks.
You can use NTILE.
Distributes the rows in an ordered partition into a specified number of groups.
Example:
SELECT col1, col2, ..., coln
FROM
(
SELECT
col1, col2, ..., coln,
NTILE(5) OVER (ORDER BY id) AS groupno
FROM yourtable
)
WHERE groupno = 3
That's a perfect use for the NTILE ranking function.
Basically, you define your query inside a CTE and add an NTILE to your rows - a number going from 1 to n (the argument to NTILE). You order your rows by some column, and then you get the n groups of rows you're looking for, and you can operate on any one of those "groups" of data.
So try something like this:
;WITH SegmentedData AS
(
SELECT
(list of your columns),
GroupNo = NTILE(5) OVER (ORDER BY SomeColumnOfYours)
FROM dbo.YourTable
)
SELECT *
FROM SegmentedData
WHERE GroupNo = 3
Of course, you can also use an UPDATE statement after the CTE to update those rows.