I have the current query that i'm running in Oracle:
WITH viewa
AS (SELECT c.columna
FROM sometable c
LEFT JOIN othertable u
ON ( c.id = u.id )
WHERE id= '111'
ORDER BY c.created_date)
SELECT columna
FROM (SELECT rownum AS row_num,
t.*
FROM viewa t)
WHERE row_num > (SELECT CASE
WHEN ( Count(*) > 100 ) THEN Count(*) - 100
ELSE 0
END AS num
FROM viewa)
the idea is to always get the first 100 rows.
as you can see, i'm creating a view at the beginning and use it twice:
in the from and in the where.
i'm doing that so i wouldn't need to fetch the first select twice and it also make the query more readable.
notice that columna is of type CLOB!!
when i'm doing the same query with other column types its working!
so its probably something related to the clob column
The weird think is that the results that im getting are empty values even though i have values in the DB!
when i'm removing the subselect in the where i'm getting the right result:
WITH viewa
AS (SELECT c.columna
FROM sometable c
LEFT JOIN othertable u
ON ( c.id = u.id )
WHERE id = '111'
ORDER BY c.created_date)
SELECT columna
FROM (SELECT rownum AS row_num,
t.*
FROM viewa t)
WHERE row_num > 0
seems like Oracle is turning the values for the Clob column "columnA" into null when using the view in the where.
is someone familiar with that?
know how to go around it ?
i solved it with a different query but i still would like to know if Oracle does change the view while fetching from it?
thank you
Without sample data this is hard but I'm guessing the reason is you're depending on rownum. Use the FETCH clause instead to limit the number of rows.
WITH viewa
AS (SELECT c.columna
FROM sometable c
LEFT JOIN othertable u ON ( c.id = u.id )
-- an order by clause should go here
FETCH FIRST 100 ROWS ONLY)
SELECT columna
FROM viewa
But you don't need that CTE at all, just do
SELECT c.columna
FROM sometable c
LEFT JOIN othertable u ON ( c.id = u.id )
-- an order by clause should go here
FETCH FIRST 100 ROWS ONLY
Note that the "first" rows are not guaranteed to be a specific set of rows unless you explicitly add an ORDER BY clause.
Since 11g does not have FETCH FIRST, you can just use rownumber as the limiting criteria. See Example at Oracle Live
select columna, created_date
from (
select c.columna, c.created_date
from sometable c
left join othertable u
on ( c.id = u.id )
where c.id = '111'
order by c.created_date
)
where rownum <= 10;
Related
I have the first table:
select COLUMN_NAME
from Emerald_Data.INFORMATION_SCHEMA.COLUMNS
where TABLE_NAME = N'tbl_Client_List_Pricing'
Don't mind the numbering in the Column_Name. I was doing this while testing because I need the order to remain as they are in the table. Not by ASC, DESC.
Anyhow, I don't know how to use the row numbers on the left that the system provides to JOIN another table without a condition.
Here is Table 2:
You can see that the left row numbers are my linking value but I don't know how to use that system index value as a condition in my JOIN.
Or if there is another way to join these two tables without a condition while keeping the Table 1 information in it's correct position and not affecting it by ORDER would be much appreciated.
Thank you!
-Chase
I guess you are looking for row_number. Use row_number to order result of two queries then join by matching order nums. Your query would be something like
with query_1 as (
select COLUMN_NAME
, rn = row_number() over (order by cast(left(COLUMN_NAME, 3) as int))
from Emerald_Data.INFORMATION_SCHEMA.COLUMNS
where TABLE_NAME = N'tbl_Client_List_Pricing'
)
, query_2 as (
select
*, rn = row_number() over (order by (select null))
from
Table_2
)
select
*
from
query_1 q1
join query_2 q2 on q1.rn = q2.rn
select COLUMN_NAME from Emerald_Data.INFORMATION_SCHEMA.COLUMNS
inner join with Table_2 on Num=cast(LEFT(COLUMN_NAME,CHARINDEX('-', COLUMN_NAME)) AS int)
where TABLE_NAME = N'tbl_Client_List_Pricing'
You could also use sys.all_columns object which could able to state the index for your desired column & JOIN them with table2
SELECT *
FROM sys.all_columns c
INNER JOIN Table2 t ON t.Num = c.column_id
WHERE OBJECT_NAME(object_id) = 'tbl_Client_List_Pricing'
I have the following data table:
Table:
ID Event
A 1
A ?
B ?
I want to write a SQL query so that I can remove duplicate ID's with preference for actual values over '?'. I can also guarantee that the only duplicates are for IDs that have a regular event (value 1-9) as well as a '?' event. So in the case above, my query should return:
ID Event
A 1
B ?
I want my query to return the rows that match this description as well as all the columns for those rows. My attempt so far is a left join:
sel L.*
from table L
left join table R
on L.ID = R.ID and
(L.Event is null and R.Event is not null)
where R.ID is null
This seems to partially work. It's able to remove duplicates but somehow for the case where there is a non duplicate ID like B with a '?" event in the above example, that row is removed. However, there are other cases where the same case is kept.
Why is this happening? I would think that might join on condition is correct since I check for when
R.Event is not null
but something is evidently wrong in my logic. Any help would be greatly appreciated.
There are multiple ways to solve this problem, but left join just doesn't come to mind.
How about this?
select t.*
from t
where event <> '?'
union all
select t.*
from t
where event = '?' and
not exists (select 1 from t t2 where t2.id = t.id and t2.event <> '?');
For these values, you could also use group by:
select id, min(event)
from t
group by id;
But aggregation would not keep all the other values in the row.
Or, a general approach to such prioritization queries is row_number():
select t.*
from (select t.*,
row_number() over (partition by id
order by (case when event = '?' then 1 else 2 end) desc
) as seqnum
from t
) t
where seqnum = 1;
In this CTE, each row in mytable can have 0 or many rows joined to it in jointable. I'm trying to returning an array_agg of the jointable's value column in this query, but I get an error saying I can't have an aggregate in a RETURNING.
WITH updated as(
UPDATE mytable SET status = 'A'
FROM
(
SELECT id FROM mytable
WHERE status = 'B'
ORDER BY mycolumn
LIMIT 100
FOR UPDATE
) sub
LEFT JOIN jointable j USING (id)
WHERE mytable.id = sub.id
GROUP BY (mytable.id)
RETURNING mytable.id, array_agg(j.value)
)
select *
from updated
ORDER BY mycolumn
You cannot have a GROUP BY clause in an UPDATE statement. Also, the UPDATE won't necessarily visit all matching rows in the joined table, so it wouldn't be able to return then anyway.
You will have to join jointable again in the outer query to get the desired result.
I'm getting the following error on my query:
here is an entry for table "table1", but it cannot be referenced from this part of the query.
This is my query:
SELECT id
FROM property_import_image_results table1
LEFT JOIN (
SELECT created_at
FROM property_import_image_results
WHERE external_url = table1.external_url
ORDER BY created_at DESC NULLS LAST
LIMIT 1
) as table2 ON (pimr.created_at = table2.created_at)
WHERE table2.created_at is NULL
You need a lateral join to be able to reference the outer table in the sub-select for the join.
You are also referencing an alias pimr in the join condition, which isn't available anywhere in the query. So you need to change that to table1 in the join condition.
You should also given the table in the inner query an alias to avoid confusion:
SELECT id
FROM property_import_image_results table1
LEFT JOIN LATERAL (
SELECT p2.created_at
FROM property_import_image_results p2
WHERE p2.external_url = table1.external_url
ORDER BY p2.created_at DESC NULLS LAST
LIMIT 1
) as table2 ON (table1.created_at = table2.created_at)
WHERE table2.created_at is NULL
Edit
This kind of query can also be solved using window functions:
select id
from (
select id,
max(created_at) over (partition by external_url) as max_created
FROM property_import_image_results
) t
where created_at <> max_created;
This might be faster than aggregating and joining as you do. But it's hard to tell. The lateral joins are quite efficient as well. It has the advantage that you can add any column you like to the result because no grouping is required.
I'm writing a page that will create a query (for non-db users) and it create the query and run it returning the results for them.
I am using row_number to handle custom pagination.
How do I do a left join and a row_number in a subquery when I don't know the specific columns I need to return. I tried to use * but I get an error that
The column '' was specified multiple times
Here is the query I tried:
SELECT * FROM
(SELECT ROW_NUMBER() OVER (ORDER BY Test) AS ROW_NUMBER, *
FROM table1 a
LEFT JOIN table2 b
ON a.ID = b.ID) x
WHERE ROW_NUMBER BETWEEN 1 AND 50
Your query is going to fail in SQL Server regardless of the row_number() call. The * returns all columns, including a.id and b.id. These both have the same name. This is fine for a query, but for a subquery, all columns need distinct names.
You can use row_number() for an arbitrary ordering by using a "subquery with constant" in the order by clause:
SELECT * FROM
(SELECT ROW_NUMBER() OVER (ORDER BY (select NULL)) AS ROW_NUMBER, *
FROM table1 a
LEFT JOIN table2 b
ON a.ID = b.ID) x
WHERE ROW_NUMBER BETWEEN 1 AND 50 ;
This removes the dependency on the underlying column name (assuming none are named ROW_NUMBER).
Try this sql. It should work.
SELECT * FROM
(SELECT ROW_NUMBER() OVER (ORDER BY a.Test) AS ROW_NUMBER, a.*,b.*
FROM table1 a
LEFT JOIN table2 b
ON a.ID = b.ID) x
WHERE ROW_NUMBER BETWEEN 1 AND 50