I am joining 2 tables using Cartesian Product as follows.
select p.type, i.amount
FROM products p, invoice i
where (p.account = i.id); -- column headers cant be changed despite having same info
This of course displays 2 columns with the respective values.
However I then want to manipulate the data further using COUNT/GROUP BY and SUM/GROUP BY but have been unable to find any relevant examples which I could get to work using 2 tables. (doing them all separately is ok, just getting them to work together is the problem).
For the end result, I want to show 3 columns showing a grouping of the 4 types, with the count of the entries falling under each type, and the total amount/SUM for each type, eg.
Type - Count of Types - Total Value
A - 5 - 500
B - 6 - 1000
C - 1 - 50
D - 2 - 100
Did you try this?
select p.type, count(p.type) Cnt, sum(i.amoumt) Total
FROM products p, invoice i
where (p.account = i.id)
group by p.type
Bear in mind that the result of a query is logically equivalent to a table or a view -- all of them are a projection of zero or more rows with one or more columns.
In general what you can do to a table in terms of select you can also do to a query or a view. Despite some limitations you can also apply deletes and updates to views and queries just as you can to a table.
If in doubt, create the query that returns the data you want, and then treat it as a table:
select type,
count(type) count_type,
sum(amount) sum(amount)
from (select ... )
group by type
Note also the subquery factoring clause, which has particular appplications if you need to reference the same logical data set multiple times:
with my_data as(
select ... )
select type,
count(type) count_type,
sum(amount) sum(amount)
from my_data
where type in (select ... from my_data)
group by type
Related
I have a distinct list of part numbers from one table. It is basically a table that contains a record of all the company's part numbers. I want to add columns that will pull data from different tables but only pertaining to the part number on that row of the distinct part list.
For example: if I have part A, B, C from the unique part list I want to add columns for Purchase quantity, repair quantity, loan quantity, etc... from three totally unique tables.
So it's almost like I need 3 subqueries that will sum of that data from the different tables for each part.
Can anybody steer me in the direction of how to do this? Please and thank you so much!
One method is correlated subqueries. Something like this:
select p.*,
(select count(*)
from purchases pu
where pu.part_id = p.part_id
) as num_purchases,
(select count(*)
from repairs r
where r.part_id = p.part_id
) as num_repairs,
(select count(*)
from loans l
where l.part_id = p.part_id
) as num_loans
from parts p;
Another option is joins with aggregation before the join. Or lateral joins (which are quite similar to correlated subqueries).
I have executed the following query:
SELECT ProductID, Quantity, Location
FROM DBLocations
ORDER BY ProductID, LocationDistanceIndex DESC;
Afterwards, I've been trying to select up to 3 closest warehouses which have each of the products - LocationDistanceIndex column (Also there could be none, 1 or 2).
How would I write the query to remain with up to 3 records for each ProductID - the 3 records with the highest LocationDistanceIndex hence the descending order by.
Also if there is a way to perform such filtering without manually written queries in MS Access, it would be great if somebody points that out.
Note: I tried using Row_Number() Over Partition but MS Access does not seem to support that.
Here is one method for MS Access:
SELECT l.*
FROM DBLocations l
WHERE l.LocationDistanceIndex IN (SELECT TOP 3 l2.LocationDistanceIndex
FROM DBLocations l2
WHERE l.ProductID = l2.ProductID
ORDER BY l2.LocationDistanceIndex DESC
);
Currently have a single table with large amount of data in access, due to the size I couldn't easily work with it in Excel any more.
I'm partially there on a query to pull data from this table.
7 Column table
One column GL_GL_NUM contains a transaction number. ~ 75% of these numbers are pairs. I'm trying to pull the records (all columns information) for each unique transaction number in this column.
I have put together some code from googling that hypothetically should work but I think I'm missing something on the syntax or simply asking access to do what it cannot.
See below:
SELECT SOURCE_FUND, GLType, Contract, Status, Debit, Credit, GL_GL_NUM
FROM Suspense
JOIN (
SELECT TC_TXN_NUM TXN_NUM, COUNT(GL_GL_NUM) GL_NUM
FROM Suspense
GROUP BY TC_TXN_NUM HAVING COUNT(GL_GL_NUM) > 1 ) SUB ON GL_GL_NUM = GL_NUM
Hey Beth is this the suggested code? It says there is a syntax error in the FROM clause. Thanks.
SELECT * from SuspenseGL
JOIN (
SELECT TC_TXN_NUM, COUNT(GL_GL_NUM) GL_NUM
FROM Suspense
GROUP BY TC_TXN_NUM
HAVING COUNT(GL_GL_NUM) > 1
Do you want detailed results (all rows and columns) or aggregate results, with one row per tx number?
If you want an aggregate result, like the count of distinct transaction numbers, then you need to apply one or more aggregate functions to any other columns you include.
If you run
SELECT TC_TXN_NUM, COUNT(GL_GL_NUM) GL_NUM
FROM Suspense
GROUP BY TC_TXN_NUM
HAVING COUNT(GL_GL_NUM) > 1
you'll get one row for each distinct txn, but if you then join those results back with your original table, you'll have the same number of rows as if you didn't join them with distinct txns at all.
Is there a column you don't want included in your results? If not, then the only query you need to work with is
select * from suspense
Considering your column names, what you may want is:
SELECT SOURCE_FUND, GLType, Contract, Status, sum(Debit) as sum_debit,
sum(Credit) as sum_credit, count(*) as txCount
FROM Suspense
group by
SOURCE_FUND, GLType, Contract, Status
based on your comments, if you can't work with aggregate results, you need to work with them all:
Select * from suspense
What's not working? It doesn't matter if 75% of the txns are duplicates, you need to send out every column in every row.
OK, let's say
Select * from suspense
returns 8 rows, and
select GL_GL_NUM from suspense group by GL_GL_NUM
returns 5 rows, because 3 of them have duplicate GL_GL_NUMs and 2 of them don't.
How many rows do you want in your result set? if you want less than 8 rows back, you need to perform some sort of aggregate function on each column you want returned.
You could do something like the following:
SELECT S.* FROM
SUSPENSE AS S
INNER JOIN (SELECT DISTINCT GL_GL_NUM, MIN(ID) AS ID FROM SUSPENSE
GROUP BY GL_GL_NUM) AS S2
ON S.ID = S2.ID
AND S.GL_GL_NUM = S2.GL_GL_NUM
Which would return a single row for a unique gl_gl_num. However if the other rows have different data it will not be shown. You would have to either aggregate that data up using SUM(Credit), SUM(Debit) and then GROUP BY the gl_gl_num.
I have attached a SQL Fiddle to demonstrate my results and make this clearer.
http://sqlfiddle.com/#!3/8284f/2
Thanks for any help in advance, I can't wrap my SQL skills around this one...
I have two tables like this:
Settings
Customerid ViewerLimit
1 50
2 50
Distribution
Customerid ServerIP
1 stream3
1 stream4
2 stream3
I want to calculate the load on each server. A customer divides the load if they have more than one server, so here customer 1 puts a load of 25 on each server. The result I'm trying to get is this:
ServerIP Load
stream3 75
stream4 25
I tried to do a sum function similar to this:
sum(viewerlimit/(count # of servers)) as load group by serverip
But I can't do a sub query within a sum function. There are many customers and possibly many servers per customer so it will become too complex to do manually. I appreciate any input.
Here is uninspired version with count in derived table:
select serverip, sum (viewerlimit/cast (ServerCount as float)) Load
from
(
select customerid, count(*) ServerCount from distribution group by customerid
) a
inner join settings
on a.customerid = settings.customerid
inner join distribution
on settings.customerid = distribution.customerid
group by serverip
Sql Fiddle to play around
UPDATE - an attempt at explanation
Derived tables are used to produce ad-hoc result sets that can be joined to main body of a query. It is placed in from clause and enclosed in parenthesis. You can use anything an ordinary select can use, top, order by, aggregate functions etc. The only thing you cannot use is correlation to a table in main body. Oh, and CTE. Derived table must be aliased.
In previous sample derived table 'a' selects counts of servers by customerid. Main body sees it as a table with CustomerId and ServerCount columns, ready to be used as any column from all listed tables. A join on customerid is performed between settings and 'a'. As this is 1:1 relation (both tables produce single row given a customerid), no duplication occurs.
How about doing a count of servers in a sub query and assign that to a query variable and then use that query variable inside the sum function?
select d.serverip, sum(s.viewerlimit/d.devider)
from (
select customerid, serverip, COUNT(serverip) over (partition by customerid) servercount
from distribution
) d
join settings s
on s.customerid=d.customerid
group by d.serverip
I am running the following queries against a database:
CREATE TEMPORARY TABLE med_error_third_party_tmp
SELECT `med_error_category`.description AS category, `med_error_third_party_category`.error_count AS error_count
FROM
`med_error_category` INNER JOIN `med_error_third_party_category` ON med_error_category.`id` = `med_error_third_party_category`.`category`
WHERE
year = 2003
GROUP BY `med_error_category`.id;
The only problem is that when I create the temporary table and do a select * on it then it returns multiple rows, but the query above only returns one row. It seems to always return a single row unless I specify a GROUP BY, but then it returns a percentage of 1.0 like it should with a GROUP BY.
SELECT category,
error_count/SUM(error_count) AS percentage
FROM med_error_third_party_tmp;
Here are the server specs:
Server version: 5.0.77
Protocol version: 10
Server: Localhost via UNIX socket
Does anybody see a problem with this that is causing the problem?
Standard SQL requires you to specify a GROUP BY clause if any column is not wrapped in an aggregate function (IE: MIN, MAX, COUNT, SUM, AVG, etc), but MySQL supports "hidden columns in the GROUP BY" -- which is why:
SELECT category,
error_count/SUM(error_count) AS percentage
FROM med_error_third_party_tmp;
...runs without error. The problem with the functionality is that because there's no GROUP BY, the SUM is the SUM of the error_count column for the entire table. But the other column values are completely arbitrary - they can't be relied upon.
This:
SELECT category,
error_count/(SELECT SUM(error_count)
FROM med_error_third_party_tmp) AS percentage
FROM med_error_third_party_tmp;
...will give you a percentage on a per row basis -- category values will be duplicated because there's no grouping.
This:
SELECT category,
SUM(error_count)/x.total AS percentage
FROM med_error_third_party_tmp
JOIN (SELECT SUM(error_count) AS total
FROM med_error_third_party_tmp) x
GROUP BY category
...will gives you a percentage per category of the sum of the categories error_count values vs the sum of the error_count values for the entire table.
another way to do it - without the temp table as seperate item...
select category, error_count/sum(error_count) "Percentage"
from (SELECT mec.description category
, metpc.error_count
FROM med_error_category mec
, med_error_third_party_category metpc
WHERE mec.id = metpc.category
AND year = 2003
GROUP BY mec.id
);
i think you will notice that the percentage is unchanging over the categories. This is probably not what you want - you probably want to group the errors by category as well.