Consider following table.
I'm trying to write a query to display - Max values for all the parts per category. Also display the date when the value was max.
So i tried this -
select Part_id, Category, max(Value), Time_Captured
from data_table
where category = 'Temperature'
group by Part_id, Category
First of all, mysql didn't throw an error for not having Time_Captured in group by.
Not sure if its a problem with mysql or my mysql.
So I assume it should return -
1 Temperature 50 11-08-2011 08:00
2 Temperature 70 11-08-2011 09:00
But its returning me the time captured from the first record of the data set i.e. 11-08-2011 07:00
Not sure where I'm going wrong. Any thoughts?
(Note: I'm running this inside a VM. Just in case if it changes anything)
You need to join to the results of a query that finds the max(value), like this:
select dt.Part_id, dt.Category, dt.Value, dt.Time_Captured
from data_table dt
join (select Part_id, Category, max(Value) as Value
from data_table group by 1, 2) x
on x.Part_id = dt.Part_id and x.Category = dt.Category
where dt.category = 'Temperature';
Note that this will return multiple rows if there are multiple rows with the same max value.
If you want to limit this to one row even though there are multiple matches for max(value), select the max(Time_Captured) (or min(Time_Captured) if you prefer), like this:
select dt.Part_id, dt.Category, dt.Value, max(dt.Time_Captured) as Time_Captured
from data_table dt
join (select Part_id, Category, max(Value) as Value
from data_table group by 1, 2) x
on x.Part_id = dt.Part_id and x.Category = dt.Category
where dt.category = 'Temperature'
group by 1, 2, 3;
Related
I have an SQL UNION command that from a large db (deaths_all), I get the the year (etos variable) and the deaths for that year (sunoloThanatwn) for 3 different scenarios, as stated in the union.
For every year, 3 rows are correctly returned. I want to calculate the sum of sunoloThanatwn, so that I have one SUM(sunoloThanatwn) per year and not 3 rows per year.
SQL UNION Query:
(
SELECT etos, sunoloThanatwn
FROM deaths_all
WHERE field = "A"
GROUP BY etos
)
UNION
(
SELECT etos, sunoloThanatwn
FROM deaths_all
WHERE field = "B"
GROUP BY etos
)
UNION
(
SELECT etos, sunoloThanatwn
FROM deaths_all
WHERE field = "C"
GROUP BY etos
)
ORDER BY etos
The query result is the following (I need a sum per year):
Just do a single aggregation query:
SELECT etos, SUM(sunoloThanatwn) AS total
FROM deaths_all
WHERE field IN ('A', 'B', 'C')
GROUP BY etos;
I think I'm missing a simple step here but I can't seem to figure it out. I've read the other threads and they talk about grouping but I can't seem to put it all together right.
I have a simple table that holds inventory transactions. In each row, there is a quantity and a price. I want to get the sum of the quantity and the sum of the each price * each quantity.
Here's my query. If I remove the grouping, I get 1 result that is multiplied by the number of rows in the table. If I add the grouping, I get the correct result multiple times. Am I missing something here? I just feel like running a query to get 20k results when they all contain the same data would be pointless.
SELECT (SUM(i.quantity) - IFNULL(SUM(s.quantity), 0)) AS quantity,
SUM(i.unitprice * i.quantity) AS totalprice
FROM 02_01_transactions t
LEFT JOIN 02_01_transactions i
ON i.type = 1
AND i.active = 1
LEFT JOIN 02_01_transactions s
ON s.type = 2
AND s.active =1
GROUP BY t.id
Not sure there is a need for the joins (you are not joining on any common value) or the type = 2 rows if you are just subtracting them out. Is there a reason the following does not work?
-- Total quantity, total price of all type 1, active transactions.
SELECT SUM(quantity) AS quantity,
SUM(unitprice * quantity) AS totalprice
FROM 02_01_transactions
WHERE type = 1
AND active = 1
Here's my guess at what you were trying to accomplish:
select
sum(quantity * case type when 1 then 1 when 2 then -1 end) as quantity,
sum(unitprice * quantity) as totalprice
from 02_01_transactions
where type in (1, 2) and active = 1
I have the following data table.
Record Date Price
A 3/1/2015 5
A 3/2/2015 6
A 3/3/2015 7
A 3/4/2015 10
B 2/1/2015 4
B 2/2/2015 6
B 2/3/2015 15
B 2/4/2015 2
How can I output a table that only shows the First price and the last price for each record for the first date in the table and the last date in the table. Output columns would be Record, First Price, Last Price. I am looking for a one step solution that is easy to implement in order to create a custom view.
The output desired would be:
Record FirstPrice LastPrice
A 5 10
B 4 2
Perhaps something like this is what you are looking for?
select R.Record, FD.Price as MinPrice, LD.Price as MaxPrice
from Records R
join (
select Price, R1.Record
from Records R1
where Date = (select MIN(DATE) from Records R2 where R2.Record = R1.Record)
) FD on FD.Record = R.Record
join (
select Price, R1.Record
from Records R1
where Date = (select MAX(DATE) from Records R2 where R2.Record = R1.Record)
) LD on LD.Record = R.Record
group by R.Record
http://sqlfiddle.com/#!9/d047b/26
Get the min and max aggregate dates grouped by the record field and join back to the root data. If you can have multiple records for the same record field on the same date, you will have to use min, max or avg to get just one value for that date.
SQLFiddle: http://sqlfiddle.com/#!9/1158b/3
SELECT anchorData.Record
, firstRecord.Price
, lastRecord.Price
FROM (
SELECT Record
, MIN(Date) AS FirstDate
, MAX(Date) AS LastDate
FROM Table1
GROUP BY Record
) AS anchorData
JOIN Table1 AS firstRecord
ON firstRecord.Record = anchorData.Record
AND firstRecord.Date = anchorData.FirstDate
JOIN Table1 AS lastRecord
ON lastRecord.Record = anchorData.Record
AND lastRecord.Date = anchorData.LastDate
"in order to create a custom view."...are you looking to do this in Oracle/MySql as a CREATE VIEW or just a query/select statement?
I would like to return a product together with its latest value and values from last hour.
I have a product-table :
id, name, type (and so on)...
I have a values-table :
id_prod, timestamp, value
Something like :
12:00:00 = 10
12:15:00 = 10
12:30:00 = 10
12:45:00 = 10
13:00:00 = 10
13:15:00 = 10
13:30:00 = 10
I would like a query that returns the latest value (13:30:00) together with the sum of values one hour back. This should return:
time = 13:30:00
latestread = 10
lasthour = 40
What I almost got working was:
SELECT *,
(SELECT value FROM values S WHERE id_prod=P.id
ORDER BY timestamp DESC LIMIT 1) as latestread,
(SELECT sum(value) FROM values WHERE id_prod=D.id and
date_created>SUBTIME(S.date_created,'01:00:00')) as trendread
FROM prod P ORDER BY name
But this fails with "Unknown column 'S.date_created' in 'where clause'"
Any suggestions?
If I understand correctly what you're trying to do, then You would have something like:
SELECT p.id, max(date_created), sum(value), mv.max_value
FROM product p
JOIN values v on p.id = v.product_id
JOIN (SELECT product_id, value as max_value
FROM values v2
WHERE date_created = (SELECT max(date_created) FROM values WHERE product_id=v2.product_id)) mv on product_id=p.id
WHERE date_created between DATE_SUB(now(), INTERVAL 1 HOUR)) and now()
GROUP BY p.id
ORDER BY p.id
Aleks G and mhasan gave solutions, but not the reason why this fails. The reason this fails is because the alias S is not known inside the subquery. Subqueries have no knowledge about the tables outside their scope.
You have missed providing alias for table Values in subquery below
SELECT *,
(SELECT value FROM values S WHERE id_prod=P.id
ORDER BY timestamp DESC LIMIT 1) as latestread,
(SELECT sum(value) FROM values S WHERE id_prod=P.id and
date_created>SUBTIME(S.date_created,'01:00:00')) as trendread
FROM prod P ORDER BY name
I think this is the query that you are trying to write:
SELECT p.*,
(SELECT v.value
FROM values v
WHERE v.id_prod = p.id
ORDER BY v.timestamp DESC
LIMIT 1
) as latestread,
(SELECT sum(v.value)
FROM values v
WHERE v.id_prod = p.id and
v.timestamp > SUBTIME(now(), '01:00:00')
) as trendread
FROM prod p
ORDER BY p.name;
This changes all the aliases to be abbreviations for the table name. It also fixes the expression for the last hour by using now() and gets rid of date_created which doesn't seem to be in either table based on the question. The query conveniently assumes that timestamp is a datetime. If it is a unix timestamp, then somewhat different time logic is necessary.
This should be reasonably efficient with an index on values(id_prod, timestamp, value).
I'm trying to select rows where a certain column does not have a certain value, such as 0, but I'm unable to get this to work.
SELECT *
FROM rentals
GROUP BY date, rooms, price
HAVING show_independently < 1
If show_independently is 1, then I don't want to group them. However, this statement shows no rows even though most rows have show_independently as 0.
SELECT date, rooms, price
FROM rentals
WHERE show_independently < 1
GROUP BY date, rooms, price
If you only want to group some rows and leave others ungrouped, you can use a UNION:
SELECT *
FROM rentals
WHERE show_independently <> 1
GROUP BY date, rooms, price
UNION ALL
SELECT *
FROM rentals
WHERE show_independently = 1
This groups only those where show_independently is not 1, and includes the rest without grouping them.
A HAVING clause is used when you are using an aggregate function to filter data.
A typical query with HAVING:
SELECT yourColumn, aggregate_function(otherColumn)
FROM yourTable
WHERE yourColumn = someValue
GROUP BY yourColumn
HAVING aggregate_function(otherColumn) = someOtherValue
I think you want to be using a WHERE clause:
SELECT date, rooms, price
FROM rentals
WHERE show_independently < 1
GROUP BY date, rooms, price