Assuming a table like this.
id town_id begin_date
12 2 2011-10-10
23 2 2011-11-10
43 2 2012-01-01
now if I do
SELECT id, MAX(begin_date) AS mx
FROM regions
The above query returns the max date but the id is wrong:
id mx
12 2012-01-01
Is this expected?
How can I get it to return the correct id (43, 2012-01-01)
If what you are trying to do is get the id associated with the MAX() date, then you can do:
SELECT id, begin_date from regions order by begin_date DESC LIMIT 1;
You forgot the GROUP BY clause:
SELECT id, MAX(begin_date) AS mx
FROM regions
GROUP BY 1
I also want to add another possible solution to this answer which might be more intuitive because the accepted answer actually is wrong and only the comment below solves it partly. Why? Because it only works if you want a grouped result by town_id. If you you need a solution which retrieves the row with the absolute maximum date you can only go with Francisco Sotos answer or the query below.
SELECT ID, begin_date from regions WHERE begin_date = (SELECT MAX(begin_date) FROM regions)
The query I posted does not use limit but instead requires a sub query. IDK which one is faster but just as an additional food for thought.
Related
To make it more clear, If I have this data in MySql:
name | allowance | age
----------------------
khan | 50 | 20
aal | 60 | 22
hyme | 50 | 21
khan | 61 | 20
notice that there are two 'khan' in the database with different allowance. I want to only show the name and the age but if I show it using the mysqli select statement, there would be two 'khan' but I only want to show only 1 'khan'. How can I do it?
You need to use GROUP_CONCAT to see agges of all Khans;
select name, GROUP_CONCAT(age) ages from Table group by name
or for minimum aged khan
select name , min(age) MiniumAge from Table group by name
or for elder khan
select name , max(age) MaxAge from Table group by name
or any khan
select name , age from Table group by name
.
Please try below query:-
SELECT name, age FROM table_name WHERE group by name
If you want any from multiple same record then simply used group by query.
I think you could do this:
SELECT name, age FROM table_name WHERE group by name,age
First thing: if both those "khan"s are the same person with two different allowances then your schema is not properly normalized and it will give you big troubles later - imagine you want to change "khan" to "Khan" - now you have to update it in multiple places instead once. Depending on your actual needs you may want one table of people (person_id, name, age), and table of allowances (person_id, allowance, [..some other parameters?..]).
Second, to really get what you want, either you use group by, to get one "random" row per each name as suggested in other answers, or you can do
SELECT DISTINCT name, age FROM table;
which will give you one row per each name-age combination, so khan-20 will be there only once - but if there were khan-25 then that is probably different person and you would have two khans returned, each with their own age.
You can try this mate:
SELECT DISTINCT
name, age
FROM
<your_table>;
or this one
SELECT
name, age
FROM
<your_table>
GROUP BY
name;
Q: Is there any chance that if there are 2 records of tha same name have difference value of age? If so, kindly update the question so that better answers will be given. Cheers!
I have a table Usage and it contains the following columns
sl_No
usage_ID
energyItem_ID
qty
unit_ID
location_ID
p_Rate
Sometimes the same EnergyItem might be located at different locations..
During those conditions how can I get the sum of qty of an individual energyItem..
How to get the sum of the qty of energyItems?
If I've understood correctly, you're trying to find the quantity of each
energy item, regardless of its location, using information in a single table.
The following query will give you the energyItem_ID of each item followed by the total quantity of each item:
SELECT energyItem_ID,Sum(qty) as TotalQuantity
FROM Usage
GROUP BY energyItem_ID
ORDER BY energyItem_ID
If, on the other hand, you wanted the quantity of each energy item, broken down by location, you would need the following:
SELECT location_ID,energyItemID,Sum(qty) as QuantityByLocation
FROM Usage
GROUP BY location_ID,energyItemID
ORDER BY location_ID,energyItemID
The order by clauses make the result easier to follow, but are not strictly necessary.
Finally, the answer by marc_s will give you the quantity of a specific energyItem.
How about:
SELECT EnergyItem_ID, SUM(qty)
FROM dbo.Usage
WHERE EnergyItem_ID = 42 -- or whatever ....
GROUP BY EnergyItem_ID
Or what are you looking for?? The question isn't very clear on the expected output....
select a.usage_ID , b.sum(p_Rate) as total from Table_1 a
inner join Table_2 as b on a.usage_ID = b.usage_ID
group by a.usage_ID
I've got a table where the columns that matter look like this:
username
source
description
My goal is to get the 10 most recent records where a user/source combination is unique. From the following data:
1 katie facebook loved it!
2 katie facebook it could have been better.
3 tom twitter less then 140
4 katie twitter Wowzers!
The query should return records 2,3 and 4 (assume higher IDs are more recent - the actual table uses a timestamp column).
My current solution 'works' but requires 1 select to generate the 10 records, then 1 select to get the proper description per row (so 11 selects to generate 10 records) ... I have to imagine there's a better way to go. That solution is:
SELECT max(id) as MAX_ID, username, source, topic
FROM events
GROUP BY source, username
ORDER BY MAX_ID desc;
It returns the proper ids, but the wrong descriptions so I can then select the proper descriptions by the record ID.
Untested, but you should be able to handle this with a join:
SELECT
fullEvent.id,
fullEvent.username,
fullEvent.source,
fullEvent.topic
FROM
events fullEvent JOIN
(
SELECT max(id) as MAX_ID, username, source
FROM events
GROUP BY source, username
) maxEvent ON maxEvent.MAX_ID = fullEvent.id
ORDER BY fullEvent.id desc;
While very easy to do in Perl or PHP, I cannot figure how to use mysql only to extract the first unique occurence of a record.
For example, given the following table:
Name Date Time Sale
John 2010-09-12 10:22:22 500
Bill 2010-08-12 09:22:37 2000
John 2010-09-13 10:22:22 500
Sue 2010-09-01 09:07:21 1000
Bill 2010-07-25 11:23:23 2000
Sue 2010-06-24 13:23:45 1000
I would like to extract the first record for each individual in asc time order.
After sorting the table is ascending time order, I need to extract the first unique record by name.
So the output would be :
Name Date Time Sale
John 2010-09-12 10:22:22 500
Bill 2010-07-25 11:23:23 2000
Sue 2010-06-24 13:23:45 1000
Is this doable in an easy fashion with mySQL?
I think that something along the lines of
select name, date, time, sale from mytable order by date, time group by name;
will get you what you're looking for
you need to perform a groupwise max or groupwise min
see below or http://pastie.org/973117 for an example
select
u.user_id,
u.username,
latest.comment_id
from
users u
left outer join
(
select
max(comment_id) as comment_id,
user_id
from
user_comment
group by
user_id
) latest on u.user_id = latest.user_id;
In databases, there really is no "first" or "last" record; think of each record as its own, non-positional entity in the table. The only positions they have are when you give them one, say, using ORDER BY.
This will give you what you want. It might not be efficient, but it works.
select Name, Date, Time, Sale from
(select Name, Date, Time, Sale from MyTable
order by Date asc, Time asc) MyTable_subquery_name
group by Name
Note: MyTable_subquery_name is just a dummy name for the subquery. MySQL will give the error ERROR 1248 (42000): Every derived table must have its own alias without it.
If only GROUP BY and ORDER BY were communicative operations, then this wouldn't have to be a subquery.
Is it possible to do a SELECT statement with a predetermined order, ie. selecting IDs 7,2,5,9 and 8 and returning them in that order, based on nothing more than the ID field?
Both these statements return them in the same order:
SELECT id FROM table WHERE id in (7,2,5,9,8)
SELECT id FROM table WHERE id in (8,2,5,9,7)
I didn't think this was possible, but found a blog entry here that seems to do the type of thing you're after:
SELECT id FROM table WHERE id in (7,2,5,9,8)
ORDER BY FIND_IN_SET(id,"7,2,5,9,8");
will give different results to
SELECT id FROM table WHERE id in (7,2,5,9,8)
ORDER BY FIND_IN_SET(id,"8,2,5,9,7");
FIND_IN_SET returns the position of id in the second argument given to it, so for the first case above, id of 7 is at position 1 in the set, 2 at 2 and so on - mysql internally works out something like
id | FIND_IN_SET
---|-----------
7 | 1
2 | 2
5 | 3
then orders by the results of FIND_IN_SET.
Your best bet is:
ORDER BY FIELD(ID,7,2,4,5,8)
...but it's still ugly.
Could you include a case expression that maps your IDs 7,2,5,... to the ordinals 1,2,3,... and then order by that expression?
All ordering is done by the ORDER BY keywords, you can only however sort ascending and descending. If you are using a language such as PHP you can then sort them accordingly using some code but I do not believe it is possible with MySQL alone.
This works in Oracle. Can you do something similar in MySql?
SELECT ID_FIELD
FROM SOME_TABLE
WHERE ID_FIELD IN(11,10,14,12,13)
ORDER BY
CASE WHEN ID_FIELD = 11 THEN 0
WHEN ID_FIELD = 10 THEN 1
WHEN ID_FIELD = 14 THEN 2
WHEN ID_FIELD = 12 THEN 3
WHEN ID_FIELD = 13 THEN 4
END
You may need to create a temp table with an autonumber field and insert into it in the desired order. Then sort on the new autonumber field.
Erm, not really. Closest you can get is probably:
SELECT * FROM table WHERE id IN (3, 2, 1, 4) ORDER BY id=4, id=1, id=2, id=3
But you probably don't want that :)
It's hard to give you any more specific advice without more information about what's in the tables.
It's hacky (and probably slow), but you can get the effect with UNION ALL:
SELECT id FROM table WHERE id = 7
UNION ALL SELECT id FROM table WHERE id = 2
UNION ALL SELECT id FROM table WHERE id = 5
UNION ALL SELECT id FROM table WHERE id = 9
UNION ALL SELECT id FROM table WHERE id = 8;
Edit: Other people mentioned the find_in_set function which is documented here.
You get answers fast around here, don't you…
The reason I'm asking this is that it's the only way I can think of to avoid sorting a complex multidimensional array. I'm not saying it would be difficult to sort, but if there were a simpler way to do it with straight sql, then why not.
One Oracle solution is:
SELECT id FROM table WHERE id in (7,2,5,9,8)
ORDER BY DECODE(id,7,1,2,2,5,3,9,4,8,5,6);
This assigns an order number to each ID. Works OK for a small set of values.
Best I can think of is adding a second Column orderColumn:
7 1
2 2
5 3
9 4
8 5
And then just do a ORDER BY orderColumn