I took this query from this question.
SELECT *
FROM A
WHERE x='abc'
OR y=0
order by case when x='abc' then 0 else 1 end;
This query supposedly will prioritize x='abc' cases. But I'm really confused why is this happening? Isn't ORDER BY followed by a column name or column number? Also, I researched on the syntax of ORDER BY and they don't tell anything about this. I also tried something like this but it says: "1st ORDER BY term out of range - should be between 1 and 1":
SELECT A
FROM B
ORDER BY 2
So, can anyone explain this query or at least point to a good documentation? Thank you very much.
Well, when an ORDER BY clause is followed by a number, this number will be referenced to the column in the (number) position.
The ORDER BY followed by a CASE EXPRESSION is called conditional ordering, each column will get the value 0 when x is equal to abc and when its not it will get the value 1. After that, the ordering is in ASC , so 0 will always be prioitized before 1.
It will be something like this:
x | y | .... | Here is the new value that will order the query
abc 1 0
ayr 0 1
acz 1 1
.........
So, basically it's like generating a new value.
Related
I have data which contains 1000+ lines and in this it contains errors people make. I have added a extra column and would like to find all duplicate Rev Names and give the first one a 1 and all remaining duplicates a 0. When there is no duplicate, it should be a 1. The outcome should look like this:
RevName ErrorCount Duplicate
Rev5588 23 1
Rev5588 67 0
Rev5588 7 0
Rev5588 45 0
Rev7895 6 1
Rev9065 4 1
Rev5588 1 1
I have tried CASE WHEN but its not giving the first one a 1, its giving them all zero's.
Thanks guys, I am pulling out my hair here trying to get this done.
You could use a case expression over the row_number window function:
SELECT RevName,
Duplicate,
CASE ROW_NUMER() OVER (PARTITION BY RevName
ORDER BY (SELECT 1)) WHEN 1 THEN 1 ELSE 0 END AS Duplicate
FROM mytable
SQL tables represent unordered sets. There is no "first" of anything, unless a column specifies the ordering.
Your logic suggests lag():
select t.*,
(case when lag(revname) over (order by ??) = revname then 0
else 1
end) as is_duplicate
from t;
The ?? is for the column that specifies the ordering.
I am having one view which is returning the following result:
I need to put identifier just like below image
Required output:
Explanation of Output: If you can see the image 1 and in that image release 1 has 3 dates. From that I need to get 1 as an identifier for the MAX(IMPL_DATE).In RELEASE_ID = 1, We are having 08/20/2016, 08/09/2016 and 10/31/2016. From This 10/31/2016 is the largest date. So, Need Identifier as 1 and other 2 are going to be 0. Same thing with the RELEASE_ID 2 we have 2 dates and from them 01/13/2017 is the largest date so, need 1 in that row and other's going to be 0.
Thanks In advance...
You can do this with window functions:
select t.*,
(case when rank() over (partition by portfolio_id, release_id
order by impl_date desc
) = 1
then 1 else 0
end) as indentifier
from t;
The above will assign "1" to all rows with the maximum date. If you want to ensure that only one row is assigned a value (even when there are ties), then use row_number() instead of rank().
SELECT * FROM tblItems
WHERE itemId IN (9,1,4)
Returns in the order that SQL finds them in (which happens to be 1, 4, 9) however, I want them returned in the order that I specified in the array.
I know I could reorder them after in my native language (obj c), but is there a neat way to do this in SQL?
Somthing like this would be great:
ORDER BY itemId (9,1,4) -- <-- this dosn't work :)
Probably the best way to do this is create a table of item IDs, which also includes a rank order. Then you can join and sort by the rank order.
Create a table like this:
itemID rank
9 1
1 2
4 3
Then your query would look like this:
select tblItems.* from tblItems
inner join items_to_get on
items_to_get.itemID = tblItems.itemID
order by rank
Use a CASE expression to map the ID values to an increasing sequence:
... ORDER BY CASE itemId
WHEN 9 THEN 1
WHEN 1 THEN 2
ELSE 3
END
I had the same task once in a mysql environment.
I ended up using
ORDER BY FIND_IN_SET(itemID, '9,1,4')
this is working for me since then. I hope it also works for sqlite
You can add a case construct to your select clause.
select case when itemid = 9 then 1
when itemid = 1 then 2 else 3 end sortfield
etc
order by sortfield
You could create a procedure to order the data in SQL, but that would be much more complicated than its native language counterpart.
There's no "neat way" to resort the data like that in SQL -- the WHERE clause of a SELECT simply says "if these criteria are matched, include the row"; it's not (and it cannot be) an ordering criterion.
I Have an SQL query giving me X results, I want the query output to have a coulmn called
count making the query somthing like this:
count id section
1 15 7
2 3 2
3 54 1
4 7 4
How can I make this happen?
So in your example, "count" is the derived sequence number? I don't see what pattern is used to determine the count must be 1 for id=15 and 2 for id=3.
count id section
1 15 7
2 3 2
3 54 1
4 7 4
If id contained unique values, and you order by id you could have this:
count id section
1 3 2
2 7 4
3 15 7
4 54 1
Looks to me like mikeY's DSum approach could work. Or you could use a different approach to a ranking query as Allen Browne described at this page
Edit: You could use DCount instead of DSum. I don't know how the speed would compare between the two, but DCount avoids creating a field in the table simply to store a 1 for each row.
DCount("*","YourTableName","id<=" & [id]) AS counter
Whether you go with DCount or DSum, the counter values can include duplicates if the id values are not unique. If id is a primary key, no worries.
I frankly don't understand what it is you want, but if all you want is a sequence number displayed on your form, you can use a control bound to the form's CurrentRecord property. A control with the ControlSource =CurrentRecord will have an always-accurate "record number" that is in sequence, and that will update when the form's Recordsource changes (which may or may not be desirable).
You can then use that number to navigate around the form, if you like.
But this may not be anything like what you're looking for -- I simply can't tell from the question you've posted and the "clarifications" in comments.
The only trick I have seen is if you have a sequential id field, you can create a new field in which the value for each record is 1. Then you do a running sum of that field.
Add to your query
DSum("[New field with 1 in it]","[Table Name]","[ID field]<=" & [ID Field])
as counterthing
That should produce a sequential count in Access which is what I think you want.
HTH.
(Stolen from Rob Mills here:
http://www.access-programmers.co.uk/forums/showthread.php?p=160386)
Alright, I guess this comes close enough to constitute an answer: the following link specifies two approaches: http://www.techrepublic.com/blog/microsoft-office/an-access-query-that-returns-every-nth-record/
The first approach assumes that you have an ID value and uses DCount (similar to #mikeY's solution).
The second approach assumes you're OK creating a VBA function that will run once for EACH record in the recordset, and will need to be manually reset (with some VBA) every time you want to run the count - because it uses a "static" value to run its counter.
As long as you have reasonable numbers (hundreds, not thousands) or records, the second approach looks like the easiest/most powerful to me.
This function can be called from each record if available from a module.
Example: incrementingCounterTimeFlaged(10,[anyField]) should provide your query rows an int incrementing from 0.
'provides incrementing int values 0 to n
'resets to 0 some seconds after first call
Function incrementingCounterTimeFlaged(resetAfterSeconds As Integer,anyfield as variant) As Integer
Static resetAt As Date
Static i As Integer
'if reset date < now() set the flag and return 0
If DateDiff("s", resetAt, Now()) > 0 Then
resetAt = DateAdd("s", resetAfterSeconds, Now())
i = 0
incrementingCounterTimeFlaged = i
'if reset date > now increments and returns
Else
i = i + 1
incrementingCounterTimeFlaged = i
End If
End Function
autoincrement in SQL
SELECT (Select COUNT(*) FROM table A where A.id<=b.id),B.id,B.Section FROM table AS B ORDER BY B.ID Asc
You can use ROW_NUMBER() which is in SQL Server 2008
SELECT ROW_NUMBER() OVER (ORDER By ID DESC) RowNum,
ID,
Section
FROM myTable
Then RowNum displays sequence of row numbers.
For example, if I did:
SELECT * FROM Users WHERE UserId BETWEEN 100 AND 1
what would the results be?
Edit: Sorry, you're right, I should have specified. I didn't want to know the exact number of rows that would return, I just wanted to know if it would return rows that were between 1 and 100 or if it would return rows from min(UserId) to 1 and 100 to max(UserId).
a BETWEEN b AND c
is shorthand for
b <= a and a <= c
So BETWEEN 100 and 1 won't match anything.
This probably depends on your RDBMS, but why not just try it out? On MySQL, I get no rows from a BETWEEN 100 AND 1 query whereas I do get rows from asking for BETWEEN 1 and 100.