I am a beginner at SQL and I am using Microsoft Access. I am trying to create count tables based on Object Def. However, some objects in Object Def have a related column that indicates how many objects are within that row. Most objects in Object Def are singular objects and are represented with a blank field.
I want the output to look something like this:
Object Def Total
Cat 3
Dog 4
Rat 4
You could use
SELECT object_def,
SUM(Nz(object_count, 1)) AS total
FROM table_name
GROUP BY object_def;
For ease of testing for your scenario: http://sqlfiddle.com/#!18/1e9d5/3
Otherwise, Group By gets you the objective you are trying to obtain.
Related
I'm extracting a table of 2000+ rows which are park details. One of the columns is JSON type. Image of the table
We have about 15 attributes like this and we also have a documentation of pre-determined codes assigned to each attribute.
Each row in the extracted table has a different set of attributes that you can see in the image. Right now, I have cast(parks.services AS text) AS "details" to get all the attributes for a particular park or extract just one of them using the code below:
CASE
WHEN cast(parks.services AS text) LIKE '%uncovered%' THEN '2'
WHEN cast(parks.services AS text) LIKE '%{covered%' THEN '1' END AS "details"
This time around, I need to extract these attributes by assigning them the codes. As an example, let's just say
Park 1 - {covered, handicap_access, elevator} to be {1,3,7}
Park 2 - {uncovered, always_open, handicap_access} to be {2,5,3}
I have thought of using subquery to pre-assign the codes, but I cannot wrap my head around JSON operators - in fact, I don't know how to extract them on 2000+ rows.
It would be helpful if someone could guide me in this topic. Thanks a lot!
You should really think about normalizing your tables. Don't store arrays. You should add a mapping table to map the parks and the attribute codes. This makes everything much easier and more performant.
step-by-step demo:db<>fiddle
SELECT
t.name,
array_agg(c.code ORDER BY elems.index) as codes -- 3
FROM mytable t,
unnest(attributes) WITH ORDINALITY as elems(value, index) -- 1
JOIN codes c ON c.name = elems.value -- 2
GROUP BY t.name
Extract the array elements into one record per element. Add the WITH ORDINALITY to save the original order.
Join your codes on the elements
Create code arrays. To ensure the correct order, you can use the index values created by the WITH ORDINALITY clause.
store_id=Store.select(:id).where(user_id:current_user.id).to_a.first
it returns id like that : Store:0x00007f8717546c30
Store.select(:id).where(user_id:current_user.id).to_a.first
select does not return an array of strings or integers for the given column(s), but rather an active record relation containing objects with just the given field:
https://apidock.com/rails/ActiveRecord/QueryMethods/select
Your code is then converting that relation to an array, and taking the first object in that array, which is an instance of the Store class. If you want the ID, then try:
Store.select(:id).where(user_id:current_user.id).to_a.first.id
However, I think you're misunderstanding how to structure the queries. Put the where part first, and then find the ID of the first result:
Store.where(user_id: current_user.id).first.id
And if there is only 1 store, then:
Store.find_by(user_id: current_user.id).id
Or...
Store.find_by(user: current_user).id
or.....
current_user.store.id
(or current_user.stores.first.id if there are many)
I have the following data in excel sheet A.
Category Name
Fruit Apple
Vegetable Brinjal
XYZ Abc
I want to create a formula which takes a value for name column, outputs the corresponding category column.
If I use VLookUp, I have to copy this reference table in each and every excel sheet wherever I need to have this operation.
Hence I am looking for something similar to
IF(input="Apple","Fruit",IF(input="Brinjal","Vegetable",IF(input="Abc",XYZ,"")))
But There is limit on nested ifs in excel and no of cases that we can have in a switch case are also limited.
I have around 200 rows of this table.
use INDEX and MATCH functions. INDEX on "category" by matching "name"
You certainly don't need so many IF statements (though I note your Q Title), for example:
=CHOOSE(MATCH(D13,{"Apple","Brinjal","Abc"},0),"Fruit","Vegetable","XYZ")
which should not grow at quite the rate your version would - but with 200 'pairs' would be getting close to the limit for CHOOSE.
(D13 as example in spreadsheet.)
Ok so I'm having a bit of a learning moment here and after figuring out A way to get this to work, I'm curious if anyone with a bit more postgres experience could help me figure out a way to do this without doing a whole lotta behind the scene rails stuff (or doing a single query for each item i'm trying to get)... now for an explaination:
Say I have 1000 records, we'll call them "Instances", in the database that have these fields:
id
user_id
other_id
I want to create a method that I can call that pulls in 10 instances that all have a unique other_id field, in plain english (I realize this won't work :) ):
Select * from instances where user_id = 3 and other_id is unique limit 10
So instead of pulling in an array of 10 instances where user_id is 3 and you can get multiple instances with the other_id is 5, I want to be able to run a map function on those 10 instances and get back something like [1,2,3,4,5,6,7,8,9,10].
In theory, I can probably do one of two things currently, though I'm trying to avoid them:
Store an array of id's and do individual calls making sure the next call says "not in this array". The problem here is I'm doing 10 individual db queries.
Pull in a large chunk of say, 50 instances and sorting through them in ruby-land to find 10 unique ones. This wouldn't allow me to take advantage of any optimizations already done in the database and I'd also run the risk of doing a query for 50 items that don't have 10 unique other_id's and I'd be stuck with those unless I did another query.
Anyways, hoping someone may be able to tell me I'm overlooking an easy option :) I know this is kind of optimizing before it's really needed but this function is going to be run over and over and over again so I figure it's not a waste of time right now.
For the record, I'm using Ruby 1.9.3, Rails 3.2.13, and Postgresql (Heroku)
Thanks!
EDIT: Just wanted to give an example of a function that technically DOES work (and is number 1 above)
def getInstances(limit, user)
out_of_instances = false
available = []
other_ids = [-1] # added -1 to avoid submitting a NULL query
until other_ids.length == limit || out_of_instances == true
instance = Instance.where("user_id IS ? AND other_id <> ALL (ARRAY[?])", user.id, other_ids).limit(1)
if instance != []
available << instance.first
other_ids << instance.first.other_id
else
out_of_instances = true
end
end
end
And you would run:
getInstances(10, current_user)
While this works, it's not ideal because it's leading to 10 separate queries every time it's called :(
In a single SQL query, it can be achieved easily with SELECT DISTINCT ON... which is a PostgreSQL-specific feature.
See http://www.postgresql.org/docs/current/static/sql-select.html
SELECT DISTINCT ON ( expression [, ...] ) keeps only the first row of
each set of rows where the given expressions evaluate to equal. The
DISTINCT ON expressions are interpreted using the same rules as for
ORDER BY (see above). Note that the "first row" of each set is
unpredictable unless ORDER BY is used to ensure that the desired row
appears first
With your example:
SELECT DISTINCT ON (other_id) *
FROM instances
WHERE user_id = 3
ORDER BY other_id LIMIT 10
Summary:
I have a list of work items that I am attempting to assign to a list of workers. Each working is allowed to only have a max of 100 work items assigned to them. Each work item specifies the user that should work it (associated as an owner).
For example:
Jim works a total of 5 accounts each with multiple work items. In total jim has 50 items to work already assigned to him. I am allowed to assign only 50 more.
My plight/goal:
I am using a temp table and a select statement to get the # of items each owner has currently assigned to them and I calculate the available slots for new items and store the values in new column. I need to be able to select from the items table where the owner matches my list of owners and their available items(in the temp table), only retrieving the number of rows for each user equal to the number of available slots per user - query would return only 50 rows for jim even though there may be 200 matching the criteria while sam may get 0 rows because he has no available slots while there are 30 items for him to work in the items table.
I realize I may be approaching this problem wrong. I want to avoid using a cursor.
Edit: Adding some example code
SELECT
nUserID_Owner
, CASE
WHEN COUNT(c.nWorkID) >= 100 THEN 0
ELSE 100 - COUNT(c.nWorkID)
END
,COUNT(c.nWorkID)
FROM tblAccounts cic
LEFT JOIN tblWorkItems c
ON c.sAccountNumber = cic.sAccountNumber
AND c.nUserID_WorkAssignedTo = cic.nUserID_Owner
AND c.nTeamID_WorkAssignedTo = cic.nTeamID_Owner
WHERE cic.nUserID_Collector IS NOT NULL
AND nUserID_CurrentOwner = 5288
AND c.bCompleted = 0
GROUP BY nUserID_Owner
This provides output vaulues of 5288, 50, 50 (in Jim's scenario)
It took longer than I wanted it to but I found a solution.
I did use a sub-query as suggested above to produce the work items with a unique row count by user.
I used PARTITION BY to produce a unique row count for each worker and included in my HAVING clause that the row number must be < the count of available slots. I'd post the code but it's beyond the char limit and I'd also have a lot of things to change to anon the system properly.
Originally I was approaching the problem incorrectly focusing on limiting the results rather than thinking about creating the necessary data to relate the result sets.