I must select CTE by the value of the window function. How, in terms of CPU, memory, choose? sequentially?
WITH t1 AS(
SELECT col1, col2, row_number() OVER(PARTITION BY col1, col2 ORDER BY col3) rn
FROM tbl
),
t2 AS(
SELECT col1, col2
FROM t1
WHERE rn = 1
)
SELECT *
FROM t2;
or nested
WITH t2 AS(
WITH t1 AS(
SELECT col1, col2, row_number() OVER(PARTITION BY col1, col2 ORDER BY col3) rn
FROM tbl
)
SELECT col1, col2
FROM t1
WHERE rn = 1
)
SELECT *
FROM t2;
EXPLAIN ANALYZE is not clear. WHERE rn = 1 in a separate CTE, because this data will be needed in several CTEs. By the execution time is almost no different.
Related
I have a view as below in PostgresSQL where if view returns no data, i have to show the column "view_lastmodifieddate" to be populated and every other column/row as empty. Again, only when the table has no data
CREATE OR REPLACE VIEW test AS
Select Column 1,
Column 2,
Column 3,
'2020-08-19 12:01:14' AS view_lastmodifieddate
From Table_1
You could use a union here:
WITH cte AS (
SELECT Col1, Col2, Col3, Col4, COUNT(*) FILTER (WHERE source = 1) OVER () AS cnt
FROM
(
SELECT Col1, Col2, Col3, Col4, 1 AS source FROM Table_1
UNION ALL
SELECT NULL, NULL, NULL, '2020-08-19 12:01:14'::timestamp, 2
) t
)
SELECT Col1, Col2, Col3, Col4
FROM cte
WHERE (cnt > 0 AND source = 1) OR (cnt = 0 AND source = 2);
If you really wanted this as a view, you could inline the CTE I provided above into the lower select query, and instead define that select as a view.
I would use a left join to accomplish this.
CREATE OR REPLACE VIEW test AS
select t.column1, t.column2, t.column3,
coalesce(t.view_lastmodifieddate, f.fixed_date) as view_lastmodifieddateb
from (values ('2020-08-19 12:01:14'::timestamp)) as f(fixed_date)
left join table_1 t
on true;
I am trying to combine two csv fields, eliminate duplicates, sort and store it in a new field.
I was able to achieve this. However, I encountered a scenario where the values are like abc and abc*. I need to keep the one with abc* and remove the other.
Could this be achieved without row by row processing?
Here is what I have.
CREATE TABLE csv_test
(
Col1 VARCHAR(100),
Col2 VARCHAR(100),
Col3 VARCHAR(500)
);
INSERT dbo.csv_test (Col1, Col2)
VALUES ('xyz,def,abc', 'abc*,tuv,def,xyz*,abc'), ('qwe,bca,a23', 'qwe,bca,a23*,abc')
--It is assumed that there are no spaces around commas
SELECT Col1, Col2, Col1 + ',' + Col2 AS Combined_NonUnique_Unsorted,
STUFF((
SELECT ',' + Item
FROM (SELECT DISTINCT Item FROM dbo.DelimitedSplit8K(Col1 + ',' + Col2,',')) t
ORDER BY Item
FOR XML PATH('')
),1,1,'') Combined_Unique_Sorted
, ExpectedResult = 'Keep the one with * and make it unique'
FROM dbo.csv_test;
--Expected Results; if there are values like abc and abc* ; I need to keep abc* and remove abc ;
--How can I achieve this without looping or using temp tables?
abc,abc*,def,tuv,xyz,xyz* -> abc*,def,tuv,xyz*
a23,a23*,abc,bca,qwe -> a23*,abc,bca,qwe
Well, since you agree that normalizing the database is the correct thing to do, I decided to try to come up with a solution for you.
I ended up with quite a cumbersome solution involving 4(!) common table expressions - cumbersome, but it works.
The first cte is to add a row identifier missing from your table - I've used ROW_NUMBER() OVER(ORDER BY Col1, Col2) for that.
The second cte is to get a unique set of values from combining both csv columns. Note that this does not handle the * part yet.
The third cte is handling the * issue.
And finally, the fourth cte is putting all the unique items back into a single csv. (I could do it in the third cte but I wanted to have each cte responsible of a single part of the solution - it's much more readable.)
Now all that's left is to update the first cte's Col3 with the fourth cte's Combined_Unique_Sorted:
;WITH cte1 as
(
SELECT Col1,
Col2,
Col3,
ROW_NUMBER() OVER(ORDER BY Col1, Col2) As rn
FROM dbo.csv_test
), cte2 as
(
SELECT rn, Item
FROM cte1
CROSS APPLY
(
SELECT DISTINCT Item
FROM dbo.DelimitedSplit8K(Col1 +','+ Col2, ',')
) x
), cte3 AS
(
SELECT rn, Item
FROM cte2 t0
WHERE NOT EXISTS
(
SELECT 1
FROM cte2 t1
WHERE t0.Item + '*' = t1.Item
AND t0.rn = t1.rn
)
), cte4 AS
(
SELECT rn,
STUFF
((
SELECT ',' + Item
FROM cte3 t1
WHERE t1.rn = t0.rn
ORDER BY Item
FOR XML PATH('')
), 1, 1, '') Combined_Unique_Sorted
FROM cte3 t0
)
UPDATE t0
SET Col3 = Combined_Unique_Sorted
FROM cte1 t0
INNER JOIN cte4 t1 ON t0.rn = t1.rn
To verify the results:
SELECT *
FROM csv_test
ORDER BY Col1, Col2
Results:
Col1 Col2 Col3
qwe,bca,a23 qwe,bca,a23*,abc a23*,abc,bca,qwe
xyz,def,abc abc*,tuv,def,xyz*,abc abc*,def,tuv,xyz*
You can see a live demo on rextester.
I found Jeff Smith's solution which is displaying differences between two tables:
SELECT MIN(TableName) as TableName, ID, COL1, COL2, COL3 ...
FROM
(
SELECT 'Table A' as TableName, A.ID, A.COL1, A.COL2, A.COL3, ...
FROM A
UNION ALL
SELECT 'Table B' as TableName, B.ID, B.COL1, B.COl2, B.COL3, ...
FROM B
) tmp
GROUP BY ID, COL1, COL2, COL3 ...
HAVING COUNT(*) = 1
ORDER BY ID
In my project I need to compare eg. col1 and col2 only, rest is used for another operations.
I tried to use
HAVING (COUNT(col1) = 1 and COUNT(col2) = 1)
but with no effect.
Could you please ptovide me solution which will do that?
Get the values of COL1 and COL2 in A that do not exist in B using EXCEPT:
SELECT COL1, COL2 FROM A
EXCEPT
SELECT COL1, COL2 FROM B
Use the results as a derived table to join them back to A and get all the columns:
SELECT 'A' AS SRC, A.COL1, A.COL2, A.COL3...
FROM (
SELECT COL1, COL2 FROM A
EXCEPT
SELECT COL1, COL2 FROM B
) AS diff
INNER JOIN A ON diff.COL1 = A.COL1 AND diff.COL2 = A.COL2
Similarly, use EXCEPT to get the values of COL1 and COL2 that exist only in B, and join the resulting set to B obtain complete rows accordingly.
Combine the two sets with UNION ALL:
SELECT 'A' AS SRC, A.COL1, A.COL2, A.COL3...
FROM (
SELECT COL1, COL2 FROM A
EXCEPT
SELECT COL1, COL2 FROM B
) AS diff
INNER JOIN A ON diff.COL1 = A.COL1 AND diff.COL2 = A.COL2
UNION ALL
SELECT 'B' AS SRC, B.COL1, B.COL2, B.COL3...
FROM (
SELECT COL1, COL2 FROM B
EXCEPT
SELECT COL1, COL2 FROM A
) AS diff
INNER JOIN B ON diff.COL1 = B.COL1 AND diff.COL2 = B.COL2
;
You are dropping the columns from the wrong place. You should drop it from the lists of columns instead of from the star:
SELECT MIN(TableName) as TableName, ID, COL1, COL2
FROM
(
SELECT 'Table A' as TableName, A.ID, A.COL1, A.COL2
FROM A
UNION ALL
SELECT 'Table B' as TableName, B.ID, B.COL1, B.COl2
FROM B
) tmp
GROUP BY ID, COL1, COL2
HAVING COUNT(*) = 1
ORDER BY ID
To keep the other columns in the result, you can use MIN (or friends) to keep them:
SELECT MIN(TableName) as TableName, ID, COL1, COL2, MIN(COL3), MIN(COL4), ...
FROM
(
SELECT 'Table A' as TableName, A.ID, A.COL1, A.COL2, A.COL3, A.COL4, ...
FROM A
UNION ALL
SELECT 'Table B' as TableName, B.ID, B.COL1, B.COL2, B.COL3, B.COL4, ...
FROM B
) tmp
GROUP BY ID, COL1, COL2
HAVING COUNT(*) = 1
ORDER BY ID
Note that this doesn't work very well for certain situations. If two rows are identical in the two tables (including IDs), then it will find it as a difference even though it's not. Also, in this version, if you have multiple rows where COL1 and COL2 are the same, then this doesn't work well either. I would join the two tables together for a more robust comparison.
I have this CTE1 that I'd like to reference it in 2 or more unrelated queries
WITH CTE1
AS
(
SELECT col1, col2, col3
FROM Table1
WHERE condition
)
SELECT * FROM CTE1;
SELECT * FROM CTE1 c // This is not working -- Invalid object name 'CTE1'.
JOIN TABLE2 t
ON c.colx = t.xolx;
Is there a way to accomplish this?
Thanks for helping
My question: I want the records without duplicate, in the same table and in multiple tables? How can I proceed to do this in SQL?
Let me explain what I have tried:
Select distinct Col1, col2
from Table
where order id = 143
Output
VolumeAnswer1 AreaAnswer1 heightAnswer1
VolumeAnswer2 AreaAnswer1 heightAnswer2
VolumeAnswer3 AreaAnswer1 heightAnswer2
Expected Output
It shows the duplicate for the second table, but I need the output to be like:
VolumeAnswer1 AreaAnswer1 heightAnswer1
VolumeAnswer2 heightAnswer2
VolumeAnswer3
I need the same scenario for multiple tables, same duplicate I found for joins also. If it cannot be handled in SQL Server, how can we handle it in .Net? I used multiple select but they used to change it in single select. Each and every column should bind in dropdownlist...
Something like this might be a good place to start:
;with cte1 as (
Select col1, cnt1
From (
Select
col1
,row_number() over(Partition by col1 Order by col1) as cnt1
From tbltest) as tbl_sub1
Where cnt1 = 1
), cte2 as (
Select col2, cnt2
From (
Select
col2
,row_number() over(Partition by col2 Order by col2) as cnt2
From tbltest) as tbl_sub2
Where cnt2 = 1
), cte3 as (
Select col3, cnt3
From (
Select
col3
,row_number() over(Partition by col3 Order by col3) as cnt3
From tbltest) as tbl_sub3
Where cnt3 = 1
)
Select
col1, col2, col3
From cte1
full join cte2 on col1 = col2
full join cte3 on col1 = col3
Sql Fiddle showing example: http://sqlfiddle.com/#!3/c9127/1