For now this is the code I'm using:
SELECT *
FROM (
SELECT product.*, rownum AS n
FROM product
) WHERE n >= 4 AND n < 4+2;
This selects 2 rows from the table product starting to count by row number 4 (included).
And it works fine BUT the final select will also show a column for the rownum.
The only workaround I have for now is to manually type the columns that I want in the main Select, but what if I didn't know the names and amount of columns?
Is there a nicer way to do this?
Many thanks
If you dont want to write all column names then you need to join your query with your table again using PK. (As I dont think that there is another way in oracle 11g to exclude rn from final result except writing all the column names manually)
SELECT T.* FROM
(SELECT PK_COLUMN
FROM (
SELECT product.PK_COLUMN, rownum AS n
FROM product
) WHERE n >= 4 AND n < 4+2) P
JOIN T ON T.PK_COLUMN = P.PK_COLUMN
Cheers!!
What I am wondering here is, you are not using any ORDER BY clause. Without using ORDER BY clause rows can be returned in any order. So basically your query is similar to -
SELECT product.*
FROM product
WHERE rownum <= 3;
Related
I am looking to combine these 2 statement into one to run as a stored procedure if possible.
I have not used temp tables in queries before and may have to with this, not sure asking advice.
I did not write the original queries and manually run the first one which returns a table listing ID's with duplicate data nad how many records. Then each record ID is put into the 2nd query to remove all but the TOP 1 based on additional filtering criteria.
I have looked at using CTE from SQL select into delete DIRECTLY but am stil at a loss on how to pass each result row ID value into the delete query.
The queries, edited for public consumption are
SELECT id, count() FROM [DEV].[dbo].[7dtest] where FileVer = 1 and CALC_DATE > FORMAT(DATEADD(DD,-7,GETDATE()), 'yyyy-MM-dd') group by id having count() > 1 order by count(*) desc
returns a table with id and number of duplicate rows
then take the id of each row and put into this delete statement
delete from [DEV].[dbo].[7dtest] where AutoID not in (
SELECT TOP 1 AutoID FROM [DEV].[dbo].[7dtest] where FileVer = 1 and id = '123' and CALC_DATE > FORMAT(DATEADD(DD,-7,GETDATE()), 'yyyy-MM-dd')
order by COMPLETED_DATE_CHECK_3 desc, COMPLETED_DATE_CHECK_2 desc, COMPLETED_DATE_CHECK_1 desc)
and FileVer = 1 and id = '123' and CALC_DATE > FORMAT(DATEADD(DD,-7,GETDATE()), 'yyyy-MM-dd')
Can this be done with CTE or do I need to create a temp table and some looping to get the ID one row at a time? Is there a better way I should be doing this?
TIA
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 am trying to find a query that would give me a count of another table in the query. The problem is that I have no idea what to set where in the count part to. As it is now it will just give back a count of all the values in that table.
Select
ID as Num,
(select Count(*) from TASK where ID=ID(Also tried Num)) as Total
from ORDER
The goal is to have a result that reads like
Num Total
_________________
1 13
2 5
3 22
You need table aliases. So I think you want:
Select ID as Num,
(select Count(*) from TASK t where t.ID = o.ID) as Total
from ORDER o;
By the way, ORDER is a terrible name for a table because it is a reserved work in SQL.
You can do it as a sub query or a join (or an OVER statement.)
I think the join is clearest when you are first learning SQL
Select
ID as Num, count(TASK.ID) AS Total
from ORDER
left join TASK ON ORDER.ID=TASK.ID
GROUP BY ORDER.ID
I am trying to select the max dates on a field with other tables, to only give me one distinct row for the max date and not other rows with other dates. the code i have for max is
SELECT DISTINCT
Cust.CustId,
LastDate=(Select Max(Convert(Date,TreatmentFieldHstry.TreatmentDateTime))
FROM TreatmentFieldHstry
WHERE Cust.CustSer = Course.CustSer
AND Course.CourseSer = Session.CourseSer
AND Session.SessionSer = TreatmentFieldHstry.SessionSer)
This gives multiple rows depending on how many dates - i just want one for the max - can anyone help with this?
Thanks
You didn't specify exactly what database and version you're using - but if you're on SQL Server 2005 or newer, you can use something like this (a CTE with the ROW_NUMBER ranking function) - I've simplified it a bit, since I don't know what those other tables are that you have in your select, that don't ever show up in any of the SELECT column lists.....
;WITH TopData AS
(
SELECT c.CustId, t.TreatmentDateTime,
ROW_NUMBER() OVER(PARTITION BY c.CustId ORDER BY t.TreatmentDateTime DESC) AS 'RowNum'
FROM
dbo.TreatmentFieldHstry t
INNER JOIN
dbo.Customer c ON c.CustId = t.CustId -- or whatever JOIN condition you have
WHERE
c.CustSer = Course.CustSer
)
SELECT
*
FROM
TopData
WHERE
RowNum = 1
Basically, the CTE (Common Table Expression) partitions your data by CustId and order by TreatmentDateTime (descending - newest first) - and numbers every entry with a consecutive number - for each "partition" (e.g. for each new value of CustId). With this, the newest entry for each customer has RowNum = 1 which is what I use to select it from that CTE.
I am using SQL server 2005.
I have a table like this -
ID Name
1 a
1 a
1 a
2 b
2 b
3 c
4 d
4 d
In this, I want to delete all duplicate entries and retain only one instance as -
ID Name
1 a
2 b
3 c
4 d
I can do this easily by adding another identity column to this table and having unique numbers in it and then deleting the duplicate records. However I want to know if I can delete the duplicate records without adding that additional column to this table.
Additionally if this can be done using only one query statement. i.e. Without using Stored procedures or temp tables.
Using a ROW_NUMBER in a CTE allows you to delete duplicate values while retaining unique rows.
WITH q AS (
SELECT RN = ROW_NUMBER() OVER (PARTITION BY ID ORDER BY ID )
, ID
, Name
FROM ATable
)
DELETE FROM q WHERE RN > 1
Lieven is Right... however you may want to tweak lieven's code by just adding a top clause in the delete statement like this:
delete top(1) from q where RN > 1;
Hope this helps
You may use this query:
delete a from
(select id,name, ROW_NUMBER() over (partition by id,name order by id) row_Count
from dup_table) a
where a.row_Count >1
delete from table1
USING table1, table1 as vtable
WHERE (NOT table1.ID=vtable.ID)
AND (table1.Name=vtable.Name)
DELETE FROM tbl
WHERE ID NOT IN (
SELECT MIN(ID)
FROM tbl
GROUP BY Name
)