I would like to write a MERGE statement to pick TOP 10 rows from a large table by using ORDER BY clause and update it’s one of the column values. MERGE statement allows me to pick TOP 10 rows but I could not put ORDER BY clause anywhere.
MERGE TOP(10) StudentAllocation AS SA
USING (SELECT #sub_id AS subId) AS TSA ON SA.sub_id = TSA.subId
WHEN MATCHED THEN
UPDATE SET SA.exam_batch = 1);
You can use a table expression as both the source and target for the MERGE.
WITH SA AS
(
SELECT TOP(10) sub_id,
exam_batch
FROM StudentAllocation
ORDER BY sub_id
)
MERGE SA
USING (SELECT #sub_id AS subId) AS TSA ON SA.sub_id = TSA.subId
WHEN MATCHED THEN
UPDATE SET SA.exam_batch = 1;
although it might be simpler to use
WITH SA AS
(
SELECT TOP(10) sub_id,
exam_batch
FROM StudentAllocation
ORDER BY sub_id
)
UPDATE SA
SET exam_batch = 1
WHERE sub_id = #sub_id;
Related
My Table, #MetaData looks like this
Table_Name Element Join_prefix
Incident hold_reason h
Incident impact i
Incident incident_state i
Incident notify n
Incident severity s
Incident state s
Change impact i
Change incident_state i
I want to update the join_prefix where it is the same, to the first 2 characters of the element, within the Table_Name. So the table looks like
Table_Name Element Join_prefix
Incident hold_reason h
Incident impact im
Incident incident_state in
Incident notify n
Incident severity se
Incident state st
Change impact im
Change incident_state in
I've been using the following sql but it updates all the rows
update #MetaData
set join_prefix=substring(element,1,2)
where exists(
select [Table_Name],[Join_prefix]
from #MetaData
group by [Table_Name],[Join_prefix]
having count(join_prefix)>1)
One method would be to use an updatable CTE. Within the CTE you can use a windowed COUNT to count how many rows have the same prefix, and then update those rows:
SELECT *
INTO dbo.YourTable
FROM (VALUES('Incident','hold_reason ',CONVERT(varchar(4),'h')),
('Incident','impact ',CONVERT(varchar(4),'i')),
('Incident','incident_state',CONVERT(varchar(4),'i')),
('Incident','notify ',CONVERT(varchar(4),'n')),
('Incident','severity ',CONVERT(varchar(4),'s')),
('Incident','state ',CONVERT(varchar(4),'s')),
('Change ','impact ',CONVERT(varchar(4),'i')),
('Change ','incident_state',CONVERT(varchar(4),'i')))V(Table_Name,Element,Join_prefix)
GO
WITH CTE AS(
SELECT Element,
Join_prefix,
COUNT(Join_prefix) OVER (PARTITION BY Join_prefix) AS C
FROM dbo.YourTable)
UPDATE CTE
SET Join_prefix = LEFT(Element,2)
WHERE C > 1;
GO
SELECT *
FROM dbo.YourTable;
GO
DROP TABLE dbo.YourTable;
Your subquery is not correlated to the outside, so it always returns true. You need a WHERE
Note that exists doesn't need to select anything, you can select 1.
Also count(*) and count(non_null_value) is the same
update m1
set join_prefix = substring(element, 1, 2)
from #MetaData m1
where exists (select 1
from #MetaData m2
where m2.join_prefix = m1.join_prefix
group by m2.Table_Name, m2.Join_prefix
having count(*) > 1
);
A better method would be an updatable CTE
with CTE as (
select *,
cnt = count(*) over (partition by m.Table_Name, m.join_prefix)
from #MetaData m
)
update CTE
set join_prefix = substring(element,1,2)
from #MetaData m1
where t.cnt > 1;
I was using below query in sql server to update the table "TABLE" using the same table "TABLE". In sql server the below query is working fine.But in DB2 its getting failed.Not sure whether I need to make any change in this query to work in DB2.
The error I am getting in DB2 is
ExampleExceptionFormatter: exception message was: DB2 SQL Error:
SQLCODE=-204, SQLSTATE=42704
This is my input Data and there you can see ENO 679 is repeating in both round 3 and round 4.
My expected output is given below. Here I am taking the ID and round value from round 4 and updating rownumber 3 with the ID value from rownumber 4.
My requirement is to find the ENO which is exist in both round 3 and round 4 and update the values accordingly.
UPDATE TGT
SET TGT.ROUND = SRC.ROUND,
TGT.ID = SRC.ID
FROM TABLE TGT INNER JOIN TABLE SRC
ON TGT.ROUND='3' and SRC.ROUND='4' and TGT.ENO = SRC.ENO
Could someone help here please. I tried something like this.But its not working
UPDATE TABLE
SET ID = (SELECT t.ID
FROM TABLE t, TABLE t2
WHERE t.ENO = t2.ENO AND t.ROUND= ='4' AND t2.ROUND='3'
) ,
ROUND= (SELECT t.ROUND
FROM TABLE t, TABLE t2
WHERE t.ENO = t2.ENO AND t.ROUND= ='4' AND t2.ROUND='3')
where ROUND='3'
You may try this. I think the issue is you are not relating your inner subquery with outer main table
UPDATE TABLE TB
SET TB.ID = (SELECT t.ID
FROM TABLE t, TABLE t2
WHERE TB.ENO=t.ENO ---- added this
and t.ENO = t2.ENO AND t.ROUND= ='4' AND t2.ROUND='3'
) ,
TB.ROUND= (SELECT t.ROUND
FROM TABLE t, TABLE t2
WHERE TB.ENO=t.ENO --- added this
and t.ENO = t2.ENO AND t.ROUND= ='4' AND t2.ROUND='3')
where tb.ROUND='3'
Try this:
UPDATE MY_SAMPLE TGT
SET (ID, ROUND) = (SELECT ID, ROUND FROM MY_SAMPLE WHERE ENO = TGT.ENO AND ROUND = 4)
WHERE ROUND = 4 AND EXISTS (SELECT 1 FROM MY_SAMPLE WHERE ENO = TGT.ENO AND ROUND = 4);
The difference with yours is that the correlated subquery has to be a row-subselect, it has to guarantee zero or one row (and will assign nulls in case of returning zero rows). The EXISTS subquery excludes rows for which the correlated subquery will not return rows.
My requirement is to compare each column of row with its previous row.
Compare row 2 with row 1
Compare row 3 with row 2
Also, if there is no difference, I need to make that column NULL. Eg: request_status_id of row 3 is same as that of row 2 so I need to update request_status_id of row 3 to NULL.
Is there a clean way to do this?
You can use the following UPDATE statement that employs LAG window function available from SQL Server 2012 onwards:
UPDATE #mytable
SET request_status_id = NULL
FROM #mytable AS m
INNER JOIN (
SELECT payment_history_id, request_status_id,
LAG(request_status_id) OVER(ORDER BY payment_history_id) AS prevRequest_status_id
FROM #mytable ) t
ON m.payment_history_id = t.payment_history_id
WHERE t.request_status_id = t.prevRequest_status_id
SQL Fiddle Demo here
EDIT:
It seems the requirement of the OP is to SET every column of the table
to NULL, in case the previous value is same as the current value. In this case the query becomes a bit more verbose. Here is an example with two columns being set. It can easily be expanded to incorporate any other column of the table:
UPDATE #mytable
SET request_status_id = CASE WHEN t.request_status_id = t.prevRequest_status_id THEN NULL
ELSE T.request_status_id
END,
request_entity_id = CASE WHEN t.request_entity_id = t.prevRequest_entity_id THEN NULL
ELSE t.request_entity_id
END
FROM #mytable AS m
INNER JOIN (
SELECT payment_history_id, request_status_id, request_entity_id,
LAG(request_status_id) OVER(ORDER BY payment_history_id) AS prevRequest_status_id,
LAG(request_entity_id) OVER(ORDER BY payment_history_id) AS prevRequest_entity_id
FROM #mytable ) t
ON m.payment_history_id = t.payment_history_id
SQL Fiddle Demo here
I have a table with set of rows with same RecordtypeCode,
then the single/set row coming from a flatfile/other source like below,
finally I need a unique row in my table by elimating the duplicate Recordtypecode & taking the max of other field information,
Finally my table should like this,
What I tried right now?
Fetching all the rows from my table & then union with the new set of records then wrote the stored procedure (using group by & max keyword) to get the desired output in temp table & finally truncate my table & then insert the temp table data to my table.
Is there is any other better ways to avoid performance issue, because i am going to play with millions of records here.
Difficult to answer without more details, but you could try something like this to get grouped results:
SELECT RecordTypeCode,
Max(AgeGroupFemale60_64),
Max(AgeGroupFemale65_69),
Max(AgeGroupFemale70_74)
FROM [TempTable]
GROUP BY RecordTypeCode
Assuming you are using SQL Server 2005+, you could use MAX() OVER to determine maximum flag values within every Recordtypecode group:
SELECT
Recordtypecode,
AgeGroupFemale60_64,
AgeGroupFemale65_69,
AgeGroupFemale70_74,
MAX(AgeGroupFemale60_64) OVER (PARTITION BY Recordtypecode),
MAX(AgeGroupFemale65_69) OVER (PARTITION BY Recordtypecode),
MAX(AgeGroupFemale70_74) OVER (PARTITION BY Recordtypecode)
FROM
dbo.TempTable
and update all the flags with those values:
WITH maximums AS (
SELECT
Recordtypecode,
AgeGroupFemale60_64,
AgeGroupFemale65_69,
AgeGroupFemale70_74,
MaxFemale60_64 = MAX(AgeGroupFemale60_64) OVER (PARTITION BY Recordtypecode),
MaxFemale65_69 = MAX(AgeGroupFemale65_69) OVER (PARTITION BY Recordtypecode),
MaxFemale70_74 = MAX(AgeGroupFemale70_74) OVER (PARTITION BY Recordtypecode)
FROM
dbo.TempTable
)
UPDATE
maximums
SET
AgeGroupFemale60_64 = MaxFemale60_64,
AgeGroupFemale65_69 = MaxFemale65_69,
AgeGroupFemale70_74 = MaxFemale70_74
;
Next, you could use ROW_NUMBER() to enumerate all the rows within the groups:
SELECT
*
rn = ROW_NUMBER() OVER (PARTITION BY Recordtypecode ORDER BY Recordtypecode)
FROM
dbo.TempTable
and delete all the rows with rn > 1:
WITH enumerated AS (
SELECT
*
rn = ROW_NUMBER() OVER (PARTITION BY Recordtypecode ORDER BY Recordtypecode)
FROM
dbo.TempTable
)
DELETE FROM
enumerated
WHERE
rn > 1
;
Alternatively, instead of the two statements, UPDATE and DELETE, you could use one, MERGE (which now assumes SQL Server 2008+), like this:
WITH enumerated AS (
SELECT
*
rn = ROW_NUMBER() OVER (PARTITION BY Recordtypecode ORDER BY Recordtypecode)
FROM
dbo.TempTable
),
maximums AS (
SELECT
Recordtypecode,
MaxFemale60_64 = MAX(AgeGroupFemale60_64),
MaxFemale65_69 = MAX(AgeGroupFemale65_69),
MaxFemale70_74 = MAX(AgeGroupFemale70_74),
rn = 1
FROM
dbo.TempTable
GROUP BY
Recordtypecode
)
MERGE INTO
enumerated AS tgt
USING
maximums AS src
ON
tgt.Recordtypecode = src.Recordtypecode AND tgt.rn = src.rn
WHEN MATCHED THEN
UPDATE SET
tgt.AgeGroupFemale60_64 = src.MaxFemale60_64,
tgt.AgeGroupFemale65_69 = src.MaxFemale65_69,
tgt.AgeGroupFemale70_74 = src.MaxFemale70_74
WHEN NOT MATCHED THEN
DELETE
;
More information:
OVER Clause (Transact-SQL)
MERGE (Transact-SQL)
Note that there are known issues with the MERGE statement that you need to be aware before deciding to use it. You can start with this article to learn more about them and see whether any of them would apply to your situation:
Use Caution with SQL Server's MERGE Statement
I have a problem which my limited SQL knowledge is keeping me from understanding.
First the problem:
I have a database which I need to run a report on, it contains configurations of a users entitlements. The report needs to show a distinct list of these configurations and a count against each one.
So a line in my DB looks like this:
USER_ID SALE_ITEM_ID SALE_ITEM_NAME PRODUCT_NAME CURRENT_LINK_NUM PRICE_SHEET_ID
37715 547 CultFREE CultPlus 0 561
the above line is one row of a users configuration, for every user ID there can be 1-5 of these lines. So the definition of a configuration is multiple rows of data sharing a common User ID with variable attributes..
I need to get a distinct list of these configurations across the whole table, leaving me just one configuration set for every instance where > 1 has that configuration and a count of instances of that configuration.
Hope this is clear?
Any ideas?!?!
I have tried various group by's and unions, also the grouping sets function to no avail.
Will be very greatful if anyone can give me some pointers!
Ouch that hurt ...
Ok so problem:
a row represents a configurable line
users may be linked to more than 1 row of configuration
configuration rows when grouped together form a configuration set
we want to figure out all of the distinct configuration sets
we want to know what users are using them.
Solution (its a bit messy but the idea is there, copy and paste in to SQL management studio) ...
-- ok so i imported the data to a table named SampleData ...
-- 1. import the data
-- 2. add a new column
-- 3. select all the values of the config in to the new column (Configuration_id)
--UPDATE [dbo].[SampleData]
--SET [Configuration_ID] = SALE_ITEM_ID + SALE_ITEM_NAME + [PRODUCT_NAME] + [CURRENT_LINK_NUM] + [PRICE_SHEET_ID] + [Configuration_ID]
-- 4. i then selected just the distinct values of those and found 6 distinct Configuration_id's
--SELECT DISTINCT [Configuration_ID] FROM [dbo].[SampleData]
-- 5. to make them a bit easier to read and work with i gave them int values instead
-- for me it was easy to do this manually but you might wanna do some trickery here to autonumber them or something
-- basic idea is to run the step 4 statement but select into a new table then add a new primary key column and set identity spec on it
-- that will generate u a bunch of incremental numbers for your config id's so u can then do something like ...
--UPDATE [dbo].[SampleData] sd
--SET Configuration_ID = (SELECT ID FROM TempConfigTable WHERE Config_ID = sd.Configuration_ID)
-- at this point you have all your existing rows with a unique ident for the values combined in each row.
-- so for example in my dataset i have several rows where only the user_id has changed but all look like this ...
--SALE_ITEM_ID SALE_ITEM_NAME PRODUCT_NAME CURRENT_LINK_NUM PRICE_SHEET_ID Configuration_ID
--54101 TravelFREE TravelPlus 0 56101 1
-- now you have a config id you can start to work on building sets up ...
-- each user is now matched with 1 or more config id
-- 6. we use a CTE (common table expression) to link the possibles (keeps the join small) ...
--WITH Temp (ConfigID)
--AS
--(
-- SELECT DISTINCT SD.Configuration_Id --SD2.Configuration_Id, SD3.Configuration_Id, SD4.Configuration_Id, SD5.Configuration_Id,
-- FROM [dbo].[SampleData] SD
--)
-- this extracts all the possible combinations using the CTE
-- on the basis of what you told me, max rows per user is 6, in the result set i have i only have 5 distinct configs
-- meaning i gain nothing by doing a 6th join.
-- cross joins basically give you every combination of unique values from the 2 tables but we joined back on the same table
-- so its every possible combination of Temp + Temp (ConfigID + ConfigID) ... per cross join so with 5 joins its every combination of
-- Temp + Temp + Temp + Temp + Temp .. good job temp only has 1 column with 5 values in it
-- 7. uncomment both this and the CTE above ... need to use them together
--SELECT DISTINCT T.ConfigID C1, T2.ConfigID C2, T3.ConfigID C3, T4.ConfigID C4, T5.ConfigID C5
--INTO [SETS]
--FROM Temp T
--CROSS JOIN Temp T2
--CROSS JOIN Temp T3
--CROSS JOIN Temp T4
--CROSS JOIN Temp T5
-- notice the INTO clause ... this dumps me out a new [SETS] table in my db
-- if i go add a primary key to this and set its ident spec i now have unique set id's
-- for each row in the table.
--SELECT *
--FROM [dbo].[SETS]
-- now here's where it gets interesting ... row 1 defines a set as being config id 1 and nothing else
-- row 2 defines set 2 as being config 1 and config 2 and nothing else ... and so on ...
-- the problem here of course is that 1,2,1,1,1 is technically the same set as 1,1,1,2,1 from our point of view
-- ok lets assign a set to each userid ...
-- 8. first we pull the distinct id's out ...
--SELECT DISTINCT USER_ID usr, null SetID
--INTO UserSets
--FROM SampleData
-- now we need to do bit a of operating on these that's a bit much for a single update or select so ...
-- 9. process findings in a loop
DECLARE #currentUser int
DECLARE #set int
-- while theres a userid not linked to a set
WHILE EXISTS(#currentUser = SELECT TOP 1 usr FROM UserSets WHERE SetId IS NULL)
BEGIN
-- figure out a set to link it to
SET #set = (
SELECT TOP 1 ID
FROM [SETS]
-- shouldn't really do this ... basically need to refactor in to a table variable then compare to that
-- that way the table lookup on ur main data is only 1 per User_id
WHERE C1 IN (SELECT DISTINCT Configuration_id FROM SampleData WHERE USER_ID = #currentUser)
AND C2 IN (SELECT DISTINCT Configuration_id FROM SampleData WHERE USER_ID = #currentUser)
AND C3 IN (SELECT DISTINCT Configuration_id FROM SampleData WHERE USER_ID = #currentUser)
AND C4 IN (SELECT DISTINCT Configuration_id FROM SampleData WHERE USER_ID = #currentUser)
AND C5 IN (SELECT DISTINCT Configuration_id FROM SampleData WHERE USER_ID = #currentUser)
)
-- hopefully that worked
IF(#set IS NOT NULL)
BEGIN
-- tell the usersets table
UPDATE UserSets SET SetId = #set WHERE usr = #currentUser
set #set = null
END
ELSE -- something went wrong ... set to 0 to prevent endless loop but any userid linked to set 0 is a problem u need to look at
UPDATE UserSets SET SetId = 0 WHERE usr = #currentUser
-- and round we go again ... until we are done
END
SELECT
USER_ID,
SALE_ITEM_ID, ETC...,
COUNT(*) WhateverYouWantToNameCount
FROM TableNAme
GROUP BY USER_ID