I am trying to learn SQL-SERVER and I have created the below query:
WITH T AS
(
SELECT ROW_NUMBER() OVER(ORDER BY d.DIALOG_ID) as row_num, *
FROM test.db as d
INNER JOIN test.dbs as ds
ON d.DIALOG_ID = ds.DIALOG_ID
)
SELECT *
FROM T
WHERE row_num <=10;
I found that the only way to limit is with ROW_NUMBER().
Although when I try to run the join I have this error:
org.jkiss.dbeaver.model.sql.DBSQLException: SQL Error [8156] [S0001]: The column 'DIALOG_ID' was specified multiple times for 'T'.
The problem: In the WITH, you do SELECT * which gets all columns from both tables db and dbs. Both have a column DIALOG_ID, so a column by that name ends up twice in the result set of the WITH.
Although until here that is all allowed, it is not good practice: why have the same data twice?
Things go wrong when SQL Server has to determine what SELECT * FROM T means: it expands SELECT * to the actual columns of T, but it finds a duplicate column name, and then it refuses to continue.
The fix (and also highly recommended in general): be specific about the columns that you want to output. If T has no duplicate columns, then SELECT * FROM T will succeed.
Note that the even-more-pure variant is to also be specific about what columns you select from T. By doing that it becomes clear at a glance what the SELECT produces, instead of having to guess or investigate when you look at the query later on (or when someone else does).
The updated code would look like this (fill in your column names as we don't know them):
WITH T AS
(
SELECT
ROW_NUMBER() OVER(ORDER BY d.DIALOG_ID) as row_num,
d.DIALOG_ID, d.SOME_OTHER_COL,
ds.DS_ID, ds.SOME_OTHER_COL_2
FROM test.db AS d
INNER JOIN test.dbs AS ds ON d.DIALOG_ID = ds.DIALOG_ID
)
SELECT row_num, DIALOG_ID, SOME_OTHER_COL, DS_ID, SOME_OTHER_COL_2
FROM T
WHERE row_num <= 10;
WITH T AS
(
SELECT ROW_NUMBER() OVER(ORDER BY d.DIALOG_ID) as row_num, d.*
FROM test.db as d
INNER JOIN test.dbs as ds
ON d.DIALOG_ID = ds.DIALOG_ID
)
SELECT *
FROM T
WHERE row_num <=10;
Related
(select ID,EXTERNAL_TRANSACTION_ID,EXTERNAL_TRANSACTION_TYPE,ROW_NUMBER() OVER(PARTITION BY EXTERNAL_TRANSACTION_ID ORDER BY ID ) AS SEQNUM
from AC_POS_TRANSACTION_TRK aptt WHERE [RESULT] ='Success'
GROUP BY ID, EXTERNAL_TRANSACTION_ID,EXTERNAL_TRANSACTION_TYPE )
Hello,
On above query, I want to get rows of transaction id's which has seqnum=1 and seqnum=2
But if that transaction id has no second row (seqnum=2), I dont want to get any row for that transaction id.
Thanks!!
Something like this
Not 100% sure if this is correct without you table definition, but my understanding is that you want to EXCLUDE records if that record has an entry with seqnum=2 -- you can't use a where clause alone because that would still return seqnum = 1.
You can use an exists /not exists or in/not in clause like this
(select ID,EXTERNAL_TRANSACTION_ID,EXTERNAL_TRANSACTION_TYPE,ROW_NUMBER() OVER(PARTITION BY EXTERNAL_TRANSACTION_ID ORDER BY ID ) AS SEQNUM
from AC_POS_TRANSACTION_TRK aptt WHERE [RESULT] ='Success'
and not exists ( select 1 from AC_POS_TRANSACTION_TRK a where a.id = aptt.id
and a.seqnum = 2)
GROUP BY ID, EXTERNAL_TRANSACTION_ID,EXTERNAL_TRANSACTION_TYPE )
basically what this does is it excludes records if a record exists as specified in the NOT EXISTS query.
One option you can try is to add a count of rows per group using the same partioning critera and then filter accordingly. Not entirely sure about your query without seeing it in context and with sample data - there's no aggregation so why use group by?
However can you try something along these lines
select * from (
select ID,EXTERNAL_TRANSACTION_ID,EXTERNAL_TRANSACTION_TYPE,
Row_Number() over(partition by EXTERNAL_TRANSACTION_ID order by ID) as SEQNUM,
Count(*) over(partition by EXTERNAL_TRANSACTION_ID) Qty
from AC_POS_TRANSACTION_TRK
where [RESULT] ='Success'
)x
where SEQNUM in (1,2) and Qty>1
This should do the job.
With Qry As (
-- Your original query goes here
),
Select Qry.*
From Qry
Where Exists (
Select *
From Qry Qry1
Where Qry1.EXTERNAL_TRANSACTION_ID = Qry.EXTERNAL_TRANSACTION_ID
And Qry1.SEQNUM = 1
)
And Exists (
Select *
From Qry Qry2
Where Qry2.EXTERNAL_TRANSACTION_ID = Qry.EXTERNAL_TRANSACTION_ID
And Qry2.SEQNUM = 2
)
BTW, your original query looks problematic to me, specifically I think that instead of a GROUP BY columns those columns should be in the PARTITION BY clause of the OVER statement, but without knowing more about the table structures and what you're trying to achieve, I could not say for sure.
I'm using SQL Server and have Management Studio installed if this is relevant.
I would like to copy a whole column from one table to another, but the catch is that the table I must copy to needs to be ordered a certain way, as there is no common identity between these tables I could use to join them.
I have read these two questions:
Copy data from one column to other column (which is in a different table)
SQL Server: UPDATE a table by using ORDER BY
and I tried to combine their answers as follows:
WITH cte AS
(
-- I must specify TOP to use ORDER BY
SELECT TOP(50000) *
FROM TableToCopyTo
ORDER BY ColumnUsedToOrder
)
UPDATE cte
SET ColumnToCopyTo = (SELECT ColumnToCopyFrom FROM TableToCopyFrom)
When I try to execute this query, it returns the following error:
Msg 512, Level 16, State 1, Line 1
Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.
I've tried looking up the error but couldn't find relevant information.
I would like to either understand why my query is wrong or find an alternative to achieve what I'm looking for.
Try the following answer. You have to give the matching columns for the two tables.
;WITH cte AS
(
-- I must specify TOP to use ORDER BY
SELECT TOP(50000) *
FROM TableToCopyTo
ORDER BY ColumnUsedToOrder
)
UPDATE cte SET ColumnToCopyTo = ColumnToCopyFrom
FROM cte
JOIN TableToCopyFrom A
ON cte.ColumnName = A.EquvaliantColumnName
Provided that your TableToCopyFrom has equal to or more rows than TableToCopyTo I'd use something like:
WITH cte1 AS
(
-- I must specify TOP to use ORDER BY
SELECT TOP(50000) *
, ROW_NUMBER() OVER (ORDER BY ColumnUsedToOrder) AS RwNr
FROM TableToCopyTo
ORDER BY ColumnUsedToOrder
), cte2 AS (
SELECT *
, ROW_NUMBER() OVER (ORDER BY (SELECT 1)) AS RwNr -- or order by a column you know makes sense; this way it'll order it the way the data "sits" in the table, but it's not guaranteed
FROM TableToCopyFrom
)
UPDATE cte1
SET ColumnToCopyTo = ColumnToCopyFrom
FROM cte1
INNER JOIN cte2 ON cte1.RwNr = cte2.RwNr;
EDIT: please make sure you test this logic on some copy of the database first of course.
you can use Row number as key as follows
WITH tblDest AS
(
SELECT Row_Number() over(order by ColumnUsedToOrder) as RowNum, TOP(50000) *
FROM TableToCopyTo
ORDER BY ColumnUsedToOrder
),tblSrc as
(
select Row_Number() over(order by (select null)) as RowNum,ColumntoCopyFrom
from TableToCopyFrom
)
update tblDest set ColumntoCopyto = ColumntoCopyFrom
FROM tblDest join tblSrc on tblDest.RowNum = tblSrc.RowNum
I can't use a Union because it's not the result I want, and I can't use join because I haven't any common column. I have tried many different SQL query structures and nothing works as I want.
I need help to achieve what I believe is a really simple SQL query. What I am doing now is
select a, b
from (select top 4 a from element_type order by c) as Y,
(SELECT * FROM (VALUES (NULL), (1), (2), (3)) AS X(b)) as Z
The first is a part of a table and the second is a hand created select that gives results like this:
select a; --Give--> a,b,c,d (1 column)
select b; --Give--> 1,2,3,4 (1 column)
I need a query based on the two first that give me (2 column) :
a,1
b,2
c,3
d,4
How can i do this? UNION, JOIN or anything else? Or maybe I can't.
All I can get for now is this:
a,1
a,2
a,3
a,4
b,1
b,2
...
If you want to join two tables together purely on the order the rows appear, then I hope your database support analytic (window) functions:
SELECT * FROM
(SELECT t.*, ROW_NUMBER() OVER(ORDER BY x) as rown FROM table1 t) t1
INNER JOIN
(SELECT t.*, ROW_NUMBER() OVER(ORDER BY x) as rown FROM table2 t) t2
ON t1.rown = t2.rown
Essentially we invent something to join them on by numbering the rows. If one of your tables already contains incrementing integers from 1, you dont need to ROW_NUMBER() OVER() on that table, because it already has suitable data to join to; you just invent a fake column of incrementing nubmers in the other table and then join together
Actually, even if it doesn't support analytics, there are ugly ways of doing row numbering, such as joining the table back to itself using id < id and COUNT(*) .. GROUP BY id to number the rows. I hate doing it, but if your DB doesnt support ROW_NUMBER i'll post an example.. :/
Bear in mind, of course, that RDBMS have R in the name for a reason - related data is.. well.. related. They don't do so well when data is unrelated, so if your hope is to join the "chalks" table to the "cheese" table even though the two are completely unrelated, you're finding out now why it's hard work! :)
Try using row_number. I've created something that might help you. See below:
declare #tableChar table(letter varchar)
insert into #tableChar(letter)
select 'a';
insert into #tableChar(letter)
select 'b';
insert into #tableChar(letter)
select 'c';
insert into #tableChar(letter)
select 'd';
select letter,ROW_NUMBER() over(order by letter ) from #tableChar
You can user row_number() to achieve this,
select a,row_number() over(order by a) as b from element_type;
As you are not taking second part from other table, so you do not need to use join. But if you are doing this on different tables the you can use row_number() to create key for both the tables and bases on those keys, you can join.
Hope it will help.
How can one filter a grouped resultset for only those groups that meet some criterion compared against the other groups? For example, only those groups that have the maximum number of constituent records?
I had thought that a subquery as follows should do the trick:
SELECT * FROM (
SELECT *, COUNT(*) AS Records
FROM T
GROUP BY X
) t HAVING Records = MAX(Records);
However the addition of the final HAVING clause results in an empty recordset... what's going on?
In MySQL (Which I assume you are using since you have posted SELECT *, COUNT(*) FROM T GROUP BY X Which would fail in all RDBMS that I know of). You can use:
SELECT T.*
FROM T
INNER JOIN
( SELECT X, COUNT(*) AS Records
FROM T
GROUP BY X
ORDER BY Records DESC
LIMIT 1
) T2
ON T2.X = T.X
This has been tested in MySQL and removes the implicit grouping/aggregation.
If you can use windowed functions and one of TOP/LIMIT with Ties or Common Table expressions it becomes even shorter:
Windowed function + CTE: (MS SQL-Server & PostgreSQL Tested)
WITH CTE AS
( SELECT *, COUNT(*) OVER(PARTITION BY X) AS Records
FROM T
)
SELECT *
FROM CTE
WHERE Records = (SELECT MAX(Records) FROM CTE)
Windowed Function with TOP (MS SQL-Server Tested)
SELECT TOP 1 WITH TIES *
FROM ( SELECT *, COUNT(*) OVER(PARTITION BY X) [Records]
FROM T
)
ORDER BY Records DESC
Lastly, I have never used oracle so apolgies for not adding a solution that works on oracle...
EDIT
My Solution for MySQL did not take into account ties, and my suggestion for a solution to this kind of steps on the toes of what you have said you want to avoid (duplicate subqueries) so I am not sure I can help after all, however just in case it is preferable here is a version that will work as required on your fiddle:
SELECT T.*
FROM T
INNER JOIN
( SELECT X
FROM T
GROUP BY X
HAVING COUNT(*) =
( SELECT COUNT(*) AS Records
FROM T
GROUP BY X
ORDER BY Records DESC
LIMIT 1
)
) T2
ON T2.X = T.X
For the exact question you give, one way to look at it is that you want the group of records where there is no other group that has more records. So if you say
SELECT taxid, COUNT(*) as howMany
GROUP by taxid
You get all counties and their counts
Then you can treat that expressions as a table by making it a subquery, and give it an alias. Below I assign two "copies" of the query the names X and Y and ask for taxids that don't have any more in one table. If there are two with the same number I'd get two or more. Different databases have proprietary syntax, notably TOP and LIMIT, that make this kind of query simpler, easier to understand.
SELECT taxid FROM
(select taxid, count(*) as HowMany from flats
GROUP by taxid) as X
WHERE NOT EXISTS
(
SELECT * from
(
SELECT taxid, count(*) as HowMany FROM
flats
GROUP by taxid
) AS Y
WHERE Y.howmany > X.howmany
)
Try this:
SELECT * FROM (
SELECT *, MAX(Records) as max_records FROM (
SELECT *, COUNT(*) AS Records
FROM T
GROUP BY X
) t
) WHERE Records = max_records
I'm sorry that I can't test the validity of this query right now.
I'm trying to limit the number of rows that would be displayed when I run my query.
When I run the code below in SQL developer, it returns missing right parenthesis error..
select * from
(select row_number() over (order by rescode) rnum, a.* from
(
SELECT *
FROM trans z
LEFT JOIN emails a
ON z.email1_hist_id=a.email_id
or z.email2_hist_id=a.email_id
) a
) where rnum between 1 and 50;
I tried running the inside query:
SELECT *
FROM trans z
LEFT JOIN emails a
ON z.email1_hist_id=a.email_id
or z.email2_hist_id=a.email_id
and it works fine. On the other hand I tried removing the OR portion of my query and included the limit rows query and it returns the number of rows I specified.
What exactly is wrong in my code?
This should work - you don't need two levels of subquery
select *
from
( SELECT *, row_number() over (order by rescode) rnum
FROM trans z
LEFT JOIN emails a
ON (z.email1_hist_id=a.email_id or z.email2_hist_id=a.email_id)
) x
where rnum between 1 and 50;
Also, make sure there are no duplicate column names between trans and emails - this will trip the query because * from the inner query cannot return duplicate names.
My best guess is that it doesn't like your giving the sub-selection an alias, so it's throwing the syntax error at the "a" in ") a )".
I don't recall about Oracle, but I know that MySQL actually requires sub-selections to have an alias. I'd try adding one to your outer sub-select (before the where rnum...).