This simple SQL problem is giving me a very hard time. Either because I'm seeing the problem the wrong way or because I'm not that familiar with SQL. Or both.
What I'm trying to do: I have a table with several columns and I only need two of them: the datetime when the entry was created and the id of the entry. Note that the hours/minutes/seconds part is important here.
However, I want to group my selection according to the DATE part only. Otherwise all groups will most likely have 1 element.
Here's my query:
SELECT MyDate as DateCr, COUNT(Id) as Occur
FROM MyTable tb WITH(NOLOCK)
GROUP BY CAST(tb.MyDate as Date)
ORDER BY DateCr ASC
However I get the following error from it:
Column "MyTable.MyDate" is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.
If I don't do the cast in the GROUP BY, everything fine. If I cast MyDate to DATE in the SELECT and keep the CAST from GROUP BY, everything fine once more. Apparently it wants to keep the same DATE or DATETIME format in the GROUP BY as in the SELECT.
My approach can be completely wrong so I am not necessarily looking to fix the above query, but to find the proper way to do it.
LE: I get the above error on line 1.
LE2: On a second look, my question indeed is not very explicit. You can ignore the above approach if it is completely wrong. Below is a sample scenario
Let me tell you what I need: I want to retrieve (1) the DateTime when each entry was created. So if I have 20 entries, then I want to get 20 DateTimes. Then if I have multiple entries created on the same DAY, I want the number of those entries. For example, let's say I created 3 entries on Monday, 1 on Tuesday and 2 today. Then from my table I need the datetimes of these 6 entries + the number of entries which were created on each day (3 for 19/03/2012, 1 for 20/03/2012 and 2 for 21/03/2012).
I'm not sure why you're objecting to performing the CONVERT in both the SELECT and the GROUP BY. This seems like a perfectly logical way to do this:
SELECT
DateCr = CONVERT(DATE, MyDate),
Occur = COUNT(Id)
FROM dbo.MyTable
GROUP BY CONVERT(DATE, MyDate)
ORDER BY DateCr;
If you want to keep the time portion of MyDate in the SELECT list, why are you bothering to group? Or how do you expect the results to look? You'll have a row for every individual date/time value, where the grouping seems to indicate you want a row for each day. Maybe you could clarify what you want with some sample data and example desired results.
Also, why are you using NOLOCK? Are you willing to trade accuracy for a haphazard turbo button?
EDIT adding a version for the mixed requirements:
;WITH d(DateCr,d,Id) AS
(
SELECT MyDate, d = CONVERT(DATE, MyDate), Id
FROM dbo.MyTable)
SELECT DateCr, Occur = (SELECT COUNT(Id) FROM d AS d2 WHERE d2.d = d.d)
FROM d
ORDER BY DateCr;
Even though this is an old post, I thought I would answer it. The solution below will work with SQL Server 2008 and above. It uses the over clause, so that the individual lines will be returned, but will also count the rows grouped by the date (without time).
SELECT MyDate as DateCr,
COUNT(Id) OVER(PARTITION BY CAST(tb.MyDate as Date)) as Occur
FROM MyTable tb WITH(NOLOCK)
ORDER BY DateCr ASC
Darren White
Related
My database is called: (training_session)
I try to print out some information from my data, but I do not want to have any duplicates. I do get it somehow, may someone tell me what I do wrong?
SELECT DISTINCT athlete_id AND duration FROM training_session
SELECT DISTINCT athlete_id, duration FROM training_session
It works perfectly if i use only one column, but when I add another. it does not work.
I think you misunderstood the use of DISTINCT.
There is big difference between using DISTINCT and GROUP BY.
Both have some sort of goal, but they have different purpose.
You use DISTINCT if you want to show a series of columns and never repeat. That means you dont care about calculations or group function aggregates. DISTINCT will show different RESULTS if you keep adding more columns in your SELECT (if the table has many columns)
You use GROUP BY if you want to show "distinctively" on a certain selected columns and you use group function to calculate the data related to it. Therefore you use GROUP BY if you want to use group functions.
Please check group functions you can use in this link.
https://dev.mysql.com/doc/refman/8.0/en/group-by-functions.html
EDIT 1:
It seems like you are trying to get the "latest" of a certain athlete, I'll assume the current scenario if there is no ID.
Here is my alternate solution:
SELECT a.athlete_id ,
( SELECT b.duration
FROM training_session as b
WHERE b.athlete_id = a.athlete_id -- connect
ORDER BY [latest column to sort] DESC
LIMIT 1
) last_duration
FROM training_session as a
GROUP BY a.athlete_id
ORDER BY a.athlete_id
This syntax is called IN-SELECT subquery. With the help of LIMIT 1, it shows the topmost record. In-select subquery must have 1 record to return or else it shows error.
MySQL's DISTINCT clause is used to filter out duplicate recordsets.
If your query was SELECT DISTINCT athlete_id FROM training_session then your output would be:
athlete_id
----------
1
2
3
4
5
6
As soon as you add another column to your query (in your example, the column called duration) then each record resulting from your query are unique, hence the results you're getting. In other words the query is working correctly.
I'm using following query:
SELECT plan.datum, plan.anketa, plan.ai as autoinc, plan.objekt as sifra , objekt.sifra, objekt.temp4_da FROM plan
LEFT JOIN objekt ON plan.objekt = objekt.sifra WHERE objekt.temp4_da = '1'
AND objekt.sifra >= 30 AND plan.datum > '2019-01-15' and plan.datum < '2019-01-30'
GROUP BY objekt.sifra
ORDER BY plan.datum ASC, plan.objekt ASC
I get results which is sorted by the last records, though I did put it sorted by date.
Results should be from 2019-01-15, but as you can see its sorted to last date plan.datum < '2019-01-30'...
How can I achive this?
EDIT:
When I select from 2019-01-15 to 2019-01-20 I achive this:
Your result comes from the ability of MySQL to process incorrect SQL queries with GROUP BY. For example, most of the DBMS is not capable to process query like this
SELECT col1, col2
FROM tab
GROUP BY col1
Some DBMS process this query if col1 is the primary key of tab, however, MySQL process it always and it returns a RANDOM col2 value if there are more than one col2 values corresponding to col1! For example, having table
col1 | col2
-----------
a | 1
a | 2
then MySQL may return (a, 1) result on Monday, and (a, 2) on Tuesday using my SQL query shown above (I'm little sarcastic).
I believe that is also your case. MySQL picks random plan.datum for each objekt.sifra (the group by attribute in your query) and you subsequently miss some plan.datum values in the result. Fix your query to obtain deterministic values and you will get rid of your problems.
Given that it does seem to have sorted how you wanted the first 4 rows shows that, those dates are all in the range specified.
You need to just go through basic diagnosis:
Does 'plan' table actually contain data with those dates?
If it does, then the data is being removed by your query.
So the next easiest to check is the WHERE, so remove the other clauses (i.e. leave the 'datum' restrictions), does that data now appear?
If it still doesn't, then the LEFT JOIN is the issue, as joins are filters too.
If you do those and the data appears, then the data and your understanding of the data don't match, and you need to check/confirm any assumptions about the data you may have made.
I'm not 100% familiar with mysql, but the GROUP BY looks really odd, your not doing any sums, mins, or operations on the group. Do you need that line?
I need to return a quantity level that happened on a certain day, but I can't add the actual day, because we're talking about hundreds of thousands of records. I need to be able to say something like:
Case When max(date) then count(quantity) end as 'Count'
I can't do this due to the aggregate not being an actual argument. Nor can I put this in my where clause, for the same reason. I have tried to write it as:
Case When max(date)=max(date) then count(quantity) end
but it doesn't work either. When I put this in my where clause, it works, but returns an incorrect count. Surely there is some way to pull data for dates. I have been searching for this for a couple of days, and the best I could find was how to write the statement to pull dates, but not to combine them with something that pulls another output.
Additionally, I need to add this to a larger query (subquery), but I don't want the larger query to filter based on this date. I do want to join it to my larger query though so it will return the quantity found for each item_number. Thanks in advance for any assistance.
This is the code that works to find the correct date and the subsequent count of pallets. But it provides different results when joined to the parent query.
(SELECT
b.item_no as 'Item No',
max(x.Date),
count(b.PKG_ID)
From
wsPKGaud a
join wspkglin b
on a.PKG_ID = b.PKG_ID
right outer Join (select
b.item_no as 'Item No',
cast(max(a.aud_dt) as date) as [Date]
from
wsPKGaud a
join wspkglin b
on a.PKG_ID = b.PKG_ID
where
a.aud_action = 'A'
group by
b.Item_no
) x
on a.aud_dt=x.Date and b.Item_no=x.[Item No]
where
a.aud_action = 'A'
and a.aud_dt=x.Date
and b.Item_no=x.[Item No]
group by
b.Item_no)
When adding to the parent query, I joined the subquery and requested max(date) and max(count) instead of continuing to ask for count(PKG_ID). The subquery already counted the PKG_ID, and when I was requesting a second count, I got a much larger output. Thanks guys!
I have a table "A" with a "date" field. I want to make a select query and order the rows with previous dates in a descending order, and then, the rows with next dates in ascending order, all in the same query. Is it possible?
For example, table "A":
id date
---------------------
a march-20
b march-21
c march-22
d march-23
e march-24
I'd like to get, having as a starting date "march-22", this result:
id date
---------------------
c march-22
b march-21
a march-20
d march-23
e march-24
In one query, because I'm doing it with two of them and it's slow, because the only difference is the sorting, and the joins I have to do are a bit "heavy".
Thanks a lot.
You could use something like this -
SELECT *
FROM test
ORDER BY IF(
date <= '2012-03-22',
DATEDIFF('2000-01-01', date),
DATEDIFF(date, '2000-01-01')
);
Here is a link to a test on SQL Fiddle - http://sqlfiddle.com/#!2/31a3f/13
That's wrong, sorry :(
From documentation:
However, use of ORDER BY for individual SELECT statements implies nothing about the order in which the rows appear in the final result because UNION by default produces an unordered set of rows. Therefore, the use of ORDER BY in this context is typically in conjunction with LIMIT, so that it is used to determine the subset of the selected rows to retrieve for the SELECT, even though it does not necessarily affect the order of those rows in the final UNION result. If ORDER BY appears without LIMIT in a SELECT, it is optimized away because it will have no effect anyway.
This should do the trick. I'm not 100% sure about adding an order in a UNION...
SELECT * FROM A where date <= now() ORDER BY date DESC
UNION SELECT * FROM A where date > now() ORDER BY date ASC
I think the real question here is how to do the joining once. Create a temporary table with the result of joining, and make the 2 selects from that table. So it will be be time consuming only on creation (once) not on select query (twice).
CREATE TABLE tmp SELECT ... JOIN -- do the heavy duty here
With this you can make the two select statenets as you originally did.
I have a table with column as and its value as given
ProvisionType------From Days------ToDays
goodLoan --------- 1------------------90
Substand ------------91--------------180
doubful--------------181--------------365
bad----------------365----------------365+
IN the following case i may have a variable which may be different and i am managing that from code....But suppose if i want to find where exactly 200 falls between From days and To Days so i get the Correct Provision Type. So please anybody could help me on this
If you're using SQL Server then this should work. Not sure if MySql has BETWEEN...
SELECT ProvisionType
FROM myTable
WHERE (myVariable BETWEEN FromDays AND ToDays)
It could also be written without the BETWEEN...
SELECT ProvisionType
FROM myTable
WHERE myVariable >= FromDays
AND myVariable <= ToDays
For this to work you should replace 365+ on the last provision with an actual number, otherwise the ToDays field will need to be a varchar field rather than numeric. Also, if a value of 365 is provided, would it be expected to fall into the last category or the one before it? The other categories have a distinct cut-off point, but the last ones overlap.
Does this work (in SQL Server):
select top 1 ProvisionType
from table
where FromDays < 200
order by FromDays desc
For MySQL:
select ProvisionType
from table
where FromDays < 200
order by FromDays desc
limit 1
I'm not sure why you need both FromDays and ToDays. That seems like you're asking for overlaps and gaps. If you just have FromDays, you guarantee no gaps or overlaps and you don't have to do clever things to manage the highest limit, ie. 365+ days.