Can Someone please help to how to write the below code in SQL Server2000? Thanks
WITH cte
AS (SELECT *,
( Row_number() OVER(ORDER BY productid, transactionid,
statusdate
DESC)
)AS
rownum
FROM #table),
cte2
AS (SELECT cte.*,
( CASE
WHEN cte.status = Isnull((SELECT t.status
FROM cte t
WHERE t.rownum = ( cte.rownum + 1
)),
'')
THEN 1
ELSE 0
END )AS rownum2
FROM cte)
SELECT cte2.productid,
cte2.transactionid,
cte2.details,
cte2.status,
cte2.statusdate,
cte2.requestdate
FROM cte2
WHERE rownum2 = 0
There is no OVER() function in 2000, so you will need to re-address/move the initial cte select. You already have a table variable #table, so I would modify this to include the row numbers, by adding a identity column.
You could then use a subquery to extract what you need from cte2.
DigbySwift's answer mentions that there is a problem with ROW_NUMBER and you need to solve that first. You can use the idea in his answer, and you could also look at answers to similar questions such as these:
ROW_NUMBER Alternative for SQL Server 2000
Row_Number simulation in Sql server 2000
However there's also another problem: SQL Server 2000 doesn't support CTEs (WITH ... AS ...).
To solve this use subselects instead of CTEs by removing the WITH clause and moving the definition of the CTE to the place(s) where it is used.
For example this query using CTEs:
WITH T1 AS (SELECT a,b,c FROM ...)
SELECT * FROM T1
Becomes:
SELECT *
FROM (
SELECT a,b,c FROM ...
) AS T1
Hopefully that is enough to get you started.
Related
How would I order the results of a SQL Server query against registered servers?
I tried:
with cte as
( select count(*) deprecatedCount
from style
where code in
( 'BYR'
,'GWP'
,'MRO'
,'STD'
,'VEF'
,'ZMK'
,'ZWR'
)
)
select * from cte order by deprecatedCount
...but the deprecatedCount column remains unsorted.
(I don't have enough reputation to include "registered" in the tags list.)
as suggested in the comments
with cte as
( select code, count(*) deprecatedCount
from style
where code in
( 'BYR'
,'GWP'
,'MRO'
,'STD'
,'VEF'
,'ZMK'
,'ZWR'
)
group by code
)
select * from cte order by deprecatedCount
I have a SQL something like this:
SELECT A,B,C,FUN(A) AS A FROM someTable
The problem is FUN() is a function which quite slow, so if there are a lot of records in someTable, there will be a big performance issue.
If we using a pagination, we can resolve this issue, we do the pagination like this:
SELECT * FROM(
SELECT A,B,C,FUN(A), Row_number()OVER( ORDER BY B ASC) AS rownum FROM someTable
)T WHERE T.rownum >=1 AND T.rownum<20
In this script, the FUN() will only execute 20 times so the performance is OK.
But we need use alias to order by, so we can't write rownum inline, have to move to sub query or CTE, we chose CTE and it looks like this:
;WITH CTE AS (
SELECT A,B AS alias,C,FUN(A) FROM someTable
)
SELECT * FROM(
SELECT *,Row_number()OVER( ORDER BY alias ASC) AS rownum FROM CTE
)T WHERE T.rownum >=1 AND T.rownum<20
So far we are going fine, we get pagination to solve performance issue, we solve the alias order problem, but somehow we need to add DISTINCT to the query:
;WITH CTE AS (
SELECT DISTINCT A,B AS alias,C,FUN(A) FROM someTable
)
SELECT * FROM(
SELECT *,Row_number()OVER( ORDER BY alias ASC) AS rownum FROM CTE
)T WHERE T.rownum >=1 AND T.rownum<20
After this, the optimize of this SQL seems gone, the FUN() will execute many times as much as the records count in someTable, we get the performance issue again.
Basically we are blocked at here, is there any suggestions?
The problem is that in order to get distinct values, the database engine must run the fun(a) function on all the records being selected.
If you do the fun(a) only in the final select, the distinct should not effect it, so it should run only on the final 20 records.
I've changed the derived table you've used to another cte (but that's a personal preference - seems to me more tidy not to mix derived tables and ctes):
;WITH CTE1 AS (
SELECT DISTINCT A,B AS alias,C
FROM someTable
),
CTE2 AS
(
SELECT *, ROW_NUMBER() OVER(ORDER BY alias) As RowNum
FROM CTE1
)
SELECT *, FUN(A)
FROM CTE2
WHERE RowNum >= 1
AND RowNum < 20
Please note that since the fun function is not deterministic you might get results that are different from your original query - so before adapting this solution compare the results first.
I have a 20 Columns Table which have duplicate value but not in all columns. that what normal distinct clause not working on it..
so i want to apply distinct on three columns (name,fname,dob) , but how? . Please give me any solution .
You could use ROW_NUMBER with a common-table-expression(CTE):
WITH CTE AS
(
SELECT t.*, RN = ROW_NUMBER() OVER (PARTITION BY name,fname,dob ORDER BY name,fname,dob)
FROM dbo.TableName t
)
SELECT * FROM CTE WHERE RN = 1
This takes one per group. Change ORDER BY name,fname,dob according to your logic.
When I use a view inside of a CTE, each subquery that references the CTE seems to re-query the view. There are large chunks of the execution plan that are repeated for each subquery. This isn't the case when selecting from a table. Is this expected? Is there any way to get around it?
WITH cte AS (
SELECT v.id
FROM test_view AS v
)
SELECT TOP 25 *,
(SELECT COUNT(*) FROM cte) AS subquery
FROM cte
I'm working with SQL Server 2005
EDIT:
I'm trying to get data from a view in pages with the query below. I need the total number of rows in the view, the number of rows that match a search, and a subset of the matching rows. This works well when selecting from tables, but using a view causes repeated execution of the CTE. I attempted to force intermediate materialization a variety of different ways from the link in Martin's answer, but didn't have any luck.
WITH tableRecords AS (
SELECT *
FROM example_view
),
filteredTableRecords AS (
SELECT *, ROW_NUMBER() OVER (ORDER BY id ASC) AS tableRecordNumber
FROM tableRecords
WHERE 1 = 1
)
SELECT *,
(SELECT COUNT(*) FROM tableRecords) AS totalRecords,
(SELECT COUNT(*) FROM filteredTableRecords) AS totalDisplayRecords
FROM filteredTableRecords
WHERE tableRecordNumber BETWEEN 1 AND 25
ORDER BY tableRecordNumber ASC
Yes it is largely expected.
See Provide a hint to force intermediate materialization of CTEs or derived tables
For the query in your question you can do this though
WITH CTE AS
(
SELECT v.id,
count(*) OVER () AS Cnt
FROM test_view AS v
)
SELECT TOP 25 *
FROM CTE
ORDER BY v.id
I suggest you re-write your query as below
There are a few improvements I did over your query
removal of where 1=1, it is unnecessary as it is always true.
the sub-query in select clause will be called everytime you execute the sql script, so instead of that you can actually use the cross apply to increase the performance.
;WITH tableRecords AS(
SELECT *
FROM example_view
),
filteredTableRecords AS (
SELECT *, ROW_NUMBER() OVER (ORDER BY id ASC) AS tableRecordNumber
FROM tableRecords
),TotalNumber
(
SELECT (SELECT COUNT(1) FROM tableRecords) AS totalRecords,
(SELECT COUNT(1) FROM filteredTableRecords) AS totalDisplayRecords
)
SELECT *
FROM filteredTableRecords F
CROSS APPLY TotalNumber AS T
WHERE tableRecordNumber BETWEEN 1 AND 25
ORDER BY tableRecordNumber ASC
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.