im currently using a subquery of an outer query to get the number of people who ordered a book ina certain time. Im a part of the way there. My current subquery is:
select count(cust_id)
from a_bkorders.order_headers
where date_format(order_date,'%Y/%m') = Prevmonth(curdate(),1)
or date_format(order_date,'%Y/%m') = PrevMonth(curdate(),2)
group by cust_id;
which returns
count(cust_id)
1
1
1
1
1
1
1
1
2
2
2
4
14
I want a count of the rows returned which is 13 but i dont think surrounding the entire subquery in count() is going to do the trick. Im sure this is an easy fix but im not seeing it.
Thanks.
(PrevMonth is a function i have written)
I think you just want count(distinct) rather than count():
select count(distinct cust_id)
from a_bkorders.order_headers
where date_format(order_date,'%Y/%m') = Prevmonth(curdate(),1) or
date_format(order_date,'%Y/%m') = PrevMonth(curdate(),2);
you should be able to just do a count of the returned results. Not sure if this will cause problems with your outer query, but if you want to post that with some sample data I can build a fiddle and fix it up real quick.
SELECT
COUNT(first_count) -- first_count is the alias i gave the subquery count. so its a count of the number of rows returned in the subquery's count
FROM(
SELECT
COUNT(cust_id) AS first_count
FROM a_bkorders.order_headers
WHERE date_format(order_date,'%Y/%m') = Prevmonth(curdate(),1)
OR date_format(order_date,'%Y/%m') = PrevMonth(curdate(),2)
GROUP BY cust_id
) AS temp; -- all tables need to have an alias
you may not even want to do a count in your subquery... unless you need the number of books that those customers ordered as well. you could just SELECT COUNT(DISTINCT cust_id) FROM.... to get the number of unique id's.
Related
I'm trying to set up a system that has a parent and 8 children. I've done this by having a table of user_id and tier_id. Now I need to get a list of all the tier_id's that appear less than 8 times, so I know that tier is incomplete and then I can go to another list and get replacements.
SELECT * FROM tiers WHERE COUNT(SELECT tier_id) < 8;
I know this isn't right, but maybe it can help explain to a genius what I'm trying to do.
First, your query needs a group by clause, with which the select clause should be consistent:
select tier_id, count(*) cnt
from tiers
group by tier_id
This gives you one row per tier_id, with the count of corresponding rows. Then, you can use a having clause to filter on the count:
select tier_id, count(*) cnt
from tiers
group by tier_id
having count(*) < 8
You have to use HAVING with GROUP BY clause.
SELECT tier_id, count(*) as TotalCount
FROM tiers
GROUP BY tier_id
HAVING TotalCount < 8
May be this will help you.
I have a table with with 2 unique linked table ids.
I get the results I want with GROUP BY but when I count I only get the number of each group.
When I do:
SELECT COUNT(id) FROM my_table GROUP BY first_linked_table_id, second_linked_table_id
I get as results 1, 2, 3, 1 but I want 4 as a result.
I tried DISTINCT but I think that only works with one column
Your requirement is to get count of number of groups. So we need two operations-
Group(inner query)
Count(outer query)
Following query will do precisely that:
SELECT COUNT(*)
FROM
(
SELECT COUNT(id)
FROM my_table
GROUP BY first_linked_table_id,
second_linked_table_id
) t
If you want to count the rows, I think you're going to need a subquery. Something like this:
SELECT COUNT(*) FROM (
SELECT COUNT(id) FROM my_table GROUP BY first_linked_table_id, second_linked_table_id
);
Problem Statement: I need my result set to include records that would not naturally return because they are NULL.
I'm going to put some simplified code here since my code seems to be too long.
Table Scores has Company_type, Company, Score, Project_ID
Select Score, Count(Project_ID)
FROM Scores
WHERE company_type= :company_type
GROUP BY Score
Results in the following:
Score Projects
5 95
4 94
3 215
2 51
1 155
Everything is working fine until I apply a condition to company_type that does not include results in one of the 5 score categories. When this happens, I don't have 5 rows in my result set any more.
It displays like this:
Score Projects
5 5
3 6
1 3
I'd like it to display like this:
Score Projects
5 5
4 0
3 6
2 0
1 3
I need the results to always display 5 rows. (Scores = 1-5)
I tried one of the approaches below by Spencer7593. My simplified query now looks like this:
SELECT i.score AS Score, IFNULL(count(*), 0) AS Projects
FROM (SELECT 5 AS score
UNION ALL
SELECT 4
UNION ALL
SELECT 3
UNION ALL
SELECT 2
UNION ALL
SELECT 1) i
LEFT JOIN Scores ON Scores.score = i.score
GROUP BY Score
ORDER BY i.score DESC
And gives the following results, which is accurate except that the rows with 1 in Projects should actually be 0 because they are derived by the "i". There are no projects with a score of 5 or 2.
Score Projects
5 1
4 5
3 6
2 1
1 3
Solved! I just needed to adjust my count to specifically look at the project count - count(project) rather than count(*). This returned the expected results.
If you always want your query to return 5 rows, with Score values of 5,4,3,2,1... you'll need a rowsource that supplies those Score values.
One approach would be to use a simple query to return those fixed values, e.g.
SELECT 5 AS score
UNION ALL SELECT 4
UNION ALL SELECT 3
UNION ALL SELECT 2
UNION ALL SELECT 1
Then use that query as inline view, and do an outer join operation to the results from your current query
SELECT i.score AS `Score`
, IFNULL(q.projects,0) AS `Projects`
FROM ( SELECT 5 AS score
UNION ALL SELECT 4
UNION ALL SELECT 3
UNION ALL SELECT 2
UNION ALL SELECT 1
) i
LEFT
JOIN (
-- the current query with "missing" Score rows goes here
-- for completeness of this example, without the query
-- we emulate that result with a different query
SELECT 5 AS score, 95 AS projects
UNION ALL SELECT 3, 215
UNION ALL SELECT 1, 155
) q
ON q.score = i.score
ORDER BY i.score DESC
It doesn't have to be the view query in this example. But there does need to be a rowsource that the rows can be returned from. You could, for example, have a simple table that contains those five rows, with those five score values.
This is just an example approach for the general approach. It might be possible to modify your existing query to return the rows you want. But without seeing the query, the schema, and example data, we can't tell.
FOLLOWUP
Based on the edit to the question, showing an example of the current query.
If we are guaranteed that the five values of Score will always appear in the Scores table, we could do conditional aggregation, writing a query like this:
SELECT s.score
, COUNT(IF(s.company_type = :company_type,s.project_id,NULL)) AS projects
FROM Scores s
GROUP BY s.score
ORDER BY s.score DESC
Note that this will require a scan of all the rows, so it may not perform as well. The "trick" is the IF function, which returns a NULL value in place of project_id, when the row would have been excluded by the WHERE clause.)
If we are guaranteed that project_id is non-NULL, we could use a more terse MySQL shorthand expression to achieve an equivalent result...
, IFNULL(SUM(s.company_type = :company_type),0) AS projects
This works because MySQL returns 1 when the comparison is TRUE, and otherwisee returns 0 or NULL.
Try something like this:
select distinct score
from (
select distinct score from scores
) s
left outer join (
Select Score, Count(Project_ID) cnt
FROM Scores
WHERE company_type= :company_type
) x
on s.score = x.score
Your posted query would not work without a group by statement. However, even there, if you don't have those particular scores for that company type, it wouldn't work either.
One option is to use an outer join. That would require a little more work though.
Here's another option using conditional aggregation:
select Score, sum(company_type=:company_type)
from Scores
group by Score
I have a MySQL table where there are many rows for each person, and I want to write a query which aggregates rows with special constraint. (one per person)
For example, lets say the table is consist of following data.
name date reason
---------------------------------------
John 2013-04-01 14:00:00 Vacation
John 2013-03-31 18:00:00 Sick
Ted 2012-05-06 20:00:00 Sick
Ted 2012-02-20 01:00:00 Vacation
John 2011-12-21 00:00:00 Sick
Bob 2011-04-02 20:00:00 Sick
I want to see the distribution of 'reason' column. If I just write a query like below
select reason, count(*) as count from table group by reason
then I will be able to see number of reasons for this table overall.
reason count
------------------
Sick 4
Vacation 2
However, I am only interested in single reason from each person. The reason that should be counted should be from a row with latest date from the person's records. For example, John's latest reason would be Vacation while Ted's latest reason would be Sick. And Bob's latest reason (and the only reason) is Sick.
The expected result for that query should be like below. (Sum of count will be 3 because there are only 3 people)
reason count
-----------------
Sick 2
Vacation 1
Is it possible to write a query such that single latest reason will be counted when I want to see distribution(count) of reasons?
Here are some facts about the table.
The table has tens of millions of rows
For most of times, each person has one reason.
Some people have multiple reasons, but 99.99% of people have fewer than 5 reasons.
There are about 30 different reasons while there are millions of distinct names.
The table is partitioned based on date range.
SELECT T.REASON, COUNT(*)
FROM
(
SELECT PERSON, MAX(DATE) AS MAX_DATE
FROM TABLE-NAME
GROUP BY PERSON
) A, TABLE-NAME T
WHERE T.PERSON = A.PERSON AND T.DATE = A.MAX_DATE
GROUP BY T.REASON
Try this
select reason, count(*) from
(select reason from table where date in
(select max(date) from table group by name)) t
group by reason
In MySQL, it's not very efficient to do this kind of query since you don't have access to tools like partitionning query in SQL Server or Oracle.
You can still emulate it by doing a subquery and retrieve the rows based on the condition you need, here the maximum date :
SELECT t.reason, COUNT(1)
FROM
(
SELECT name, MAX(adate) AS maxDate
FROM #aTable
GROUP BY name
) maxDateRows
INNER JOIN #aTable t ON maxDateRows.name = t.name
AND maxDateRows.maxDate = t.adate
GROUP BY t.reason
You can see a sample here.
Test this query on your samples, but I'm afraid that it will be slow as hell.
For your information, you can do the same thing in a more elegant and much much faster way in SQL Server :
SELECT reason, COUNT(1)
FROM
(
SELECT name
, reason
, RANK() OVER(PARTITION BY name ORDER BY adate DESC) as Rank
FROM #aTable
) AS rankTable
WHERE Rank = 1
GROUP BY reason
The sample is here
If you are really stuck to MySql, and the first query is too slow, then you can split the problem.
Do a first query creating a table:
CREATE TABLE maxDateRows AS
SELECT name, MAX(adate) AS maxDate
FROM #aTable
GROUP BY name
Then create index on both name and maxDate.
Finally, get the results :
SELECT t.reason, COUNT(1)
FROM maxDateRows m
INNER JOIN #aTable t ON m.name = t.name
AND m.maxDate = t.adate
GROUP BY t.reason
The solution you are looking for seems to be solved by this query :
select
reason,
count(*)
from (select * from tablename group by name) abc
group by
reason
It is quite fast and simple. You can view the SQL Fiddle
Apologies if this answer duplicates an existing. Maybe I'm suffering from some form aphasia but I cannot see it...
SELECT x.reason
, COUNT(*)
FROM absentism x
JOIN
( SELECT name,MAX(date) max_date FROM absentism GROUP BY name) y
ON y.name = x.name
AND y.max_date = x.date
GROUP
BY reason;
I am trying to list several products on a page. My query returns multiples of the same product and I am trying to figure out how to limit it to one only with my query.
The primary key on the first table that we will call table_one is ID.
The second table has a column of ProductID that references the primary key on table_one.
My query brings me back multiples of my ProductID that is equal to 6 below. I just want one result to be brought back, BUT I still want my all of my data in DateReserved on table_two to be queried. Pretty sure I need to add one more thing to my query, but I have not had much luck.
The results I want back are as follows.
ID Productname Quantity Image Date Reserved SumQuantity
6 productOne 6 'image.jpg' 03-31-2013 3
7 productTwo 1 'product.jpg' 04-04-2013 1
Here is my first table. table_one
ID Productname Quantity Image
6 productOne 6 'image.jpg'
7 productTwo 1 'product.jpg'
Here is my second table. table_two
ID ProductID DateReserved QuantityReserved
1 6 03-31-2013 3
2 6 04-07-2013 2
3 7 04-04-2013 1
Here is my query that I am trying to use.
SELECT *
FROM `table_one`
LEFT JOIN `table_two`
ON `table_one`.`ID` = `table_two`.`ProductID`
WHERE `table_one`.`Quantity` > 0
OR `table_two`.`DateReserved` + INTERVAL 5 DAY <= '2013-03-27'
ORDER BY ProductName
Sorry for posting another answer, but as it seems my first try on it was not so good ;)
To only get one result row per reservation you need to sum them up somehow.
First I suggest you explicitly select the columns you want back in your result and don't use "*".
I suggest you try something like this:
SELECT
`table_one`.`ID`, `table_one`.`Productname`, `table_one`.`Image`, `table_one`.`Quantity`,
`table_two`.`ProductID`, SUM(`table_two`.`QuantityReserved`)
FROM
`table_one`
LEFT JOIN
`table_two` ON `table_one`.`ID` = `table_two`.`ProductID`
WHERE
`table_one`.`Quantity` > 0
OR `table_two`.`DateReserved` + INTERVAL 5 DAY <= '2013-03-27'
GROUP BY `table_two`.`ProductID`
ORDER BY ProductName
As you see I used "SUM" to get a combined quantity, this is called aggregation and the "GROUP BY" helps you getting rid of multiple occurences of the same ProductID.
One problem that you have now is that you will have to get the reservation date from a seperate query (well at least I am now unsure how you would get it into the same query)
Since you are using MySQL
LIMIT <NUMBER>
should exactly do what you want, you just insert it after your ORDER BY clause, but probably you should also add one more ordering to that, so you can be sure that you will always get the one entity that you wanted and not just some "random" entity ;)
So without further ordering your query would look like this:
SELECT
*
FROM `table_one`
LEFT JOIN `table_two` ON `table_one`.`ID` = `table_two`.`ProductID`
WHERE
`table_one`.`Quantity` > 0
OR `table_two`.`DateReserved` + INTERVAL 5 DAY <= '2013-03-27'
ORDER BY ProductName
LIMIT 1
here some more description about that
SELECT a.member_id,a.member_name,a.gender,a.amount,b.trip_id,b.location
FROM tbl_member a
LEFT JOIN (SELECT trip_id, MAX(amount) as amount FROM tbl_member GROUP BY trip_id ) b ON a.trip_id= b.trip_id
LEFT JOIN tbl_trip b ON a.trip_id=c.trip_id
ORDER BY member_name