I am facing a problem with MySQL query which is a variant of "Id for row with max value". I am either getting error or incorrect result for all my trials.
Here is the table structure
Row_id
Group_id
Grp_col1
Grp_col2
Field_for_aggregate_func
Another_field_for_row
For all rows with a particular group_id, I want to group by fields Grp_col1, Grp_col2 then get max value of Field_for_aggregate_func and then corresponding value of Another_field_for_row.
Query I have tried is like below
SELECT c.*
FROM mytable as c left outer join mytable as c1
on (
c.group_id=c1.group_id and
c.Grp_col1 = c1.Grp_col1 and
c.Grp_col2 = c1.Grp_col2 and
c.Field_for_aggregate_func > c1.Field_for_aggregate_func
)
where c.group_id=2
Among alternative solutions for this problem I want a high performance solution as this will be used for large set of data.
EDIT: Here is the sample set of row and expected answer
Group_ID Grp_col1 Grp_col2 Field_for_aggregate_func Another_field_for_row
2 -- N 12/31/2015 35
2 -- N 1/31/2016 15 select 15 from group for max value 1/31/2016
2 -- Y 12/31/2015 5
2 -- Y 1/1/2016 15
2 -- Y 1/2/2016 25
2 -- Y 1/3/2016 30 select 30 from group for max value 1/3/2016
You can use a sub-query to find the maximums, then join that with the original table, along the lines of:
select m1.group_id, m1.grp_col1, m1.grp_col2, m1.another_field_for_row, max_value
from mytable m1, (
select group_id, grp_col1, grp_col2, max(field_for_aggregate_func) as max_value
from mytable
group by group_id, grp_col1, grp_col2) as m2
where m1.group_id=m2.group_id
and m1.grp_col1=m2.grp_col1
and m1.grp_col2=m2.grp_col2
and m1.field_for_aggregate_func=m2.max_value;
Watch out for when there is more than one max_value for the given grouping. You'll get multiple rows for that grouping. Fiddle here.
Try this.
See Fiddle demo here
http://sqlfiddle.com/#!9/9a3c26/8
Select t1.* from table1 t1 inner join
(
Select a.group_id,a.grp_col2,
A.Field_for_aggregate_func,
count(*) as rnum from table1 a
Inner join table1 b
On a.group_id=b.group_id
And a.grp_col2=b.grp_col2
And a.Field_for_aggregate_func
<=b.Field_for_aggregate_func
Group by a.group_id,
a.grp_col2,
a.Field_for_aggregate_func) t2
On t1.group_id=t2.group_id
And t1.grp_col2=t2.grp_col2
And t1.Field_for_aggregate_func
=t2.Field_for_aggregate_func
And t2.rnum=1
Here first I am assigning a rownumber in descending order based on date. The selecting all the records for that date.
Related
I have a table like this
I want to check the all rows in Column A with column B and get the count of duplicates.
For example, I want to get the
count of 12 as 3(2 times in A+1 time in B)
count of 11 as 2(2 times in A+0 time in B)
count of 13 as 2(1 time in A+0 time in B)
How can I acheive it?
You can calculate the total occurrences from a union all. A where clause can show only the values that occur in the A column:
select nr
, count(*)
from (
select A as nr
from YourTable
union all
select B
from YourTable
) sub
where nr in -- only values that occur at least once in the A column
(
select A
from YourTable
)
group by
nr
having count(*) > 1 -- show only duplicates
You can combine all values in A and B then do the group by.
Then only select those values found in column A.
Select A, count(A) as cnt
From (
Select A
from yourTable
Union All
Select B
from yourTable) t
Where t.A in
(select distinct A from yourTable)
Group by t.A
Order by t.A;
Result:
A cnt
11 2
12 3
13 1
See demo: http://sqlfiddle.com/#!9/9fcfe9/3
This question already has answers here:
SQL select only rows with max value on a column [duplicate]
(27 answers)
Closed 5 years ago.
I have a table where each ID is repeated 3 times. there is a date in front of each id in each row.
I want to select entire row for each ID where date is latest.
There are total 370 columns in this table i want all columns to get selected when i select that row.
Sample -
ID Name Date Marks .. .. ..
1 XY 4/3/2017 27
1 fv 4/3/2014 98
1 jk 4/3/2016 09
2 RF 4/12/2015 87
2 kk 4/3/2009 56
2 PP 4/3/2011 76
3 ee 4/3/2001 12
3 ppp 4/3/2003 09
3 lll 4/3/2011 23
The Answer should be
ID Name Date Marks .. .. ..
1 XY 4/3/2017 27
2 RF 4/12/2015 87
3 lll 4/3/2011 23
I am attempting as below -
select distinct ID,*,max(date) as maxdate from table
Also i am trying this in Hive . so not sure if some sql functions dont work in Hive
Thanks
This question has been asked before. Please see this question.
Using the accepted answer and adapting it to your problem you get:
SELECT tt.*
FROM myTable tt
INNER JOIN
(SELECT ID, MAX(Date) AS MaxDateTime
FROM myTable
GROUP BY ID) groupedtt
ON tt.ID = groupedtt.ID
AND tt.Date = groupedtt.MaxDateTime
One way is:
select table.*
from table
join
(
select ID, max(Date) as max_dt
from table
group by ID
) t
on table.ID= t.ID and table.Date = t.max_dt
Note that if you have multiple equally higher dates for same ID, then you will get all those rows in result
You can do this with a Correlated Subquery (That is a subquery wherein you reference a field in the main query). In this case:
SELECT *
FROM yourtable t1
WHERE date = (SELECT max(date) from yourtable WHERE id = t1.id)
Here we give the yourtable table an alias of t1 and then use that alias in the subquery grabbing the max(date) from the same table yourtable for that id.
You can use a join to do this
SELECT t1.* from myTable t1
LEFT OUTER JOIN myTable t2 on t2.ID=t1.ID AND t2.`Date` > t1.`Date`
WHERE t2.`Date` IS NULL;
Only rows which have the latest date for each ID with have a NULL join to t2.
Here's one way. The inner query gets the max date for each id. Then you can join that back to your main table to get the rows that match.
select
*
from
<your table>
inner join
(select id, max(<date col> as max_date) m
where yourtable.id = m.id
and yourtable.datecolumn = m.max_date)
Have you tried the following:
SELECT ID, COUNT(*), max(date)
FROM table
GROUP BY ID;
TableA contains data from id's 55,66,68,70.
My Query:
select id, count(id) as total from TableA where id in (10,22,43,55,66) group by id
Output:
id total
55 2
66 5
Desired Output:
id total
10 0
22 0
43 0
55 2
66 5
Is there a way I can rewrite this query and have an isnull to 0 for the values in the IN statement that are not in the table? For example, 10,22, and 43 are not in tableA but are in the IN statement, so I want the total for those values to be 0
UPDATE: I forgot to mention the values from the IN statement are passed to the query as in array from the client application. So the values are constantly different so I cant hard code anything
You can't do this with in. You can do this with a left join:
select t.id, count(a.id)
from (select 10 as id union all select 22 union all select 43 union all
select 55 union all select 66
) t left join
tableA a
on a.id = t.id
group by t.id;
CREATE a Table Variable and then use that
DECLARE #Ids TABLE (id int, PRIMARY KEY(id))
INSERT #Ids(id) VALUES (10),(22),(43),(55),(66)
SELECT i.id, ISNULL(COUNT(id),0)
FROM #ids i
LEFT JOIN TableA ta ON ta.id = i.id
GROUP BY i.id
If your ID's are within a reasonable range then you can create a recursive call to build a table containing all possible id values and the IN clause will filter it down to only the values you want. Then join that result set with the original table to get your count:
WITH AllNumbers AS (
SELECT 0 AS x
UNION ALL
SELECT x+1 FROM AllNumbers WHERE x < 100
)
SELECT an.x, COUNT(id)
FROM
TableA ta
RIGHT JOIN AllNumbers an ON ta.id = an.x
WHERE an.x IN (10,22,43,55,66)
GROUP BY an.x
OPTION (maxrecursion 100)
You can adjust the '100' values to a higher number but it creates a call stack within SQL that will hit a limit at some point.
Alternatively, if you have an existing table that contains all possible ids then join to that instead of 'AllNumbers' and eliminate the recursion.
Otherwise there may be some regex options to pivot the set into rows and then use the same join statement above.
I hope you can help me with this one. I've been looking for ways to set up a MySQL query that selects rows based on the number of times a certain value occurs, but have had no luck so far. I'm pretty sure i need to use count(*) somewhere, but i can only found how to count all values or all distinct values, instead of counting all occurences.
I have a table as such:
info setid
-- --
A 1
B 1
C 2
D 1
E 2
F 3
G 1
H 3
What i need is a query that will select all the lines where a setid occurs a certain number (x) of times.
So using x=2 should give me
C 2
E 2
F 3
H 3
because both setIds 2 and 3 each occur two times. Using x=1 or x = 3 should not give any results, and choosing x=4 should give me
A 1
B 1
D 1
G 1
Because only setid 1 occurs 4 times.
I hope you guys can help me. At this point i've been looking for the answer for so long that i'm not even sure this can be done in MySQL anymore. :)
select * from mytable
where setid in (
select setid from mytable
group by setid
having count(*) = 2
)
you can specify the # of times a setid needs to occur in the table in the having count(*) part of the subquery
Consider the following statement that uses an uncorrelated subquery:
SELECT ... FROM t1 WHERE t1.a IN (SELECT b FROM t2);
The optimizer rewrites the statement to a correlated subquery:
SELECT ... FROM t1 WHERE EXISTS (SELECT 1 FROM t2 WHERE t2.b = t1.a);
If the inner and outer queries return M and N rows, respectively, the execution time becomes on the order of O(M×N), rather than O(M+N) as it would be for an uncorrelated subquery.
But this time the subquery in Fuzzy Tree's solution is complety superfluous:
SELECT
set_id,
GROUP_CONCAT(info ORDER BY info) infos
COUNT(*) total
FROM
tablename
GROUP_BY set_id
HAVING COUNT(*) = 2
I have a MySQL table like this
id Name count
1 ABC 1
2 CDF 3
3 FGH 4
using simply select query I get the values as
1 ABC 1
2 CDF 3
3 FGH 4
How I can get the result like this
1 ABC 1
2 CDF 3
3 FGH 4
4 NULL 0
You can see Last row. When Records are finished an extra row in this format
last_id+1, Null ,0 should be added. You can see above. Even I have no such row in my original table. There may be N rows not fixed 3,4
The answer is very simple
select (select max(id) from mytable)+1 as id, NULL as Name, 0 as count union all select id,Name,count from mytable;
This looks a little messy but it should work.
SELECT a.id, b.name, coalesce(b.`count`) as `count`
FROM
(
SELECT 1 as ID
UNION
SELECT 2 as ID
UNION
SELECT 3 as ID
UNION
SELECT 4 as ID
) a LEFT JOIN table1 b
ON a.id = b.id
WHERE a.ID IN (1,2,3,4)
UPDATE 1
You could simply generate a table that have 1 column preferably with name (ID) that has records maybe up 10,000 or more. Then you could simply join it with your table that has the original record. For Example, assuming that you have a table named DummyRecord with 1 column and has 10,000 rows on it
SELECT a.id, b.name, coalesce(b.`count`) as `count`
FROM DummyRecord a LEFT JOIN table1 b
ON a.id = b.id
WHERE a.ID >= 1 AND
a.ID <= 4
that's it. Or if you want to have from 10 to 100, then you could use this condition
...
WHERE a.ID >= 10 AND
a.ID <= 100
To clarify this is how one can append an extra row to the result set
select * from table union select 123 as id,'abc' as name
results
id | name
------------
*** | ***
*** | ***
123 | abc
Simply use mysql ROLLUP.
SELECT * FROM your_table
GROUP BY Name WITH ROLLUP;
select
x.id,
t.name,
ifnull(t.count, 0) as count
from
(SELECT 1 AS id
-- Part of the query below, you will need to generate dynamically,
-- just as you would otherwise need to generate 'in (1,2,3,4)'
UNION ALL SELECT 2
UNION ALL SELECT 3
UNION ALL SELECT 4
UNION ALL SELECT 5
) x
LEFT JOIN YourTable t
ON t.id = x.id
If the id does not exist in the table you're selecting from, you'll need to LEFT JOIN against a list of every id you want returned - this way, it will return the null values for ones that don't exist and the true values for those that do.
I would suggest creating a numbers table that is a single-columned table filled with numbers:
CREATE TABLE `numbers` (
id int(11) unsigned NOT NULL
);
And then inserting a large amount of numbers, starting at 1 and going up to what you think the highest id you'll ever see plus a thousand or so. Maybe go from 1 to 1000000 to be on the safe side. Regardless, you just need to make sure it's more-than-high enough to cover any possible id you'll run into.
After that, your query can look like:
SELECT n.id, a.*
FROM
`numbers` n
LEFT JOIN table t
ON t.id = n.id
WHERE n.id IN (1,2,3,4);
This solution will allow for a dynamically growing list of ids without the need for a sub-query with a list of unions; though, the other solutions provided will equally work for a small known list too (and could also be dynamically generated).