I am using knex and bookshelf, and my table consists of author, title, content, count, and each data looks like this:
author: 'John Doe',
title: 'aaaaa',
content: 'aaaaaaaa'
count: 54,
I want to retrieve data based on the value of count, and I want to get 4 data that has the highest count value.
If I want to retrieve all data, I am doing like this:
router.get('/', (req, res) => {
Article.forge().fetchAll().then(article => {
res.json(article);
})
})
Is there any way that I can do like forge({ count: 3 data that has the highest count value }) or
What should I add the code so that I can achieve this?
Combine orderBy with fetchPage
Article
.orderBy('-count')
.fetchPage({
pageSize: 3
})
.forge()
This highlights a reason why my team is removing bookshelf and just using basic knex. Unless you are wanting to fetch related models it's simpler to deal without the ORM layer. The knex equivalent knex code is:
knex('articles')
.orderBy('count', 'desc')
.limit(3)
Which is slightly simpler and the resulting rows' properties can be accessed directly, ie rows[0].id rather than rows[0].get('id')
Related
I'm running a database on sequelize and sqlite and I use soft-deletes to basically archive the data.
I'm aware that with .findAll(paranoid: false) I can find all rows including the soft deleted ones. However I would like to find ONLY the soft-deleted ones.
Is there any way to achieve this? Or is there perhaps a way to do "set operations" with two data results, like finding the relative complement of one in the other?
For this, you can add the following condition to where.
deletedAt: { [Op.not]: null }
For example like this:
const projects = await db.Project.findAndCountAll({
paranoid: false,
order: [['createdAt', 'DESC']],
where: { employer_id: null, deletedAt: { [Op.not]: null } },
limit: parseInt(size),
offset: (page - 1) * parseInt(size),
});
In my first attempt to develop something in Ruby on Rails :) ... I have a list of names stored in fields "first_name" and "last_name". In my Person model, I have defined something like this:
def sort_name
sort_name = last_name + ',' + first_name
end
Now I want to show all persons shown in a list, sorted by sort_name, but (in my controller) something like
#persons = Person.order(:sort_name)
doesn't work (Unknown column 'sort_name' in 'order clause'). How do reference to the calculated field sort_name in my controller?
I am sure this is a "oh my god I am so stupid moment" but happy for any advise!
If the model Person has the fields name, first_lastname and second_lastname, you can do the next:
Person.order(:name, :first_lastname, :second_lastname)
By default is ordering in ascending way. Also you can put if you want ascending or descending way for each field:
Person.order(name: :asc, first_lastname: :desc, second_lastname: :asc)
Additional if you want add a column with the complete name, you can use select, using postgresql the code would be:
people = Person.order(
name: :asc, first_lastname: :desc, second_lastname: :asc
).select(
"*, concat(name,' ', first_lastname, ' ',second_lastname) as sort_name"
)
people[0].sort_name
# the sort_name can be for example "Adán Saucedo Salas"
I'm new to DynamoDB and I'm trying to query a table from javascript using the Dynamoose library. I have a table with a primary partition key of type String called "id" which is basically a long string with a user id. I have a second column in the table called "attributes" which is a DynamoDB map and is used to store arbitrary user attributes (I can't change the schema as this is how a predefined persistence adapter works and I'm stuck working with it for convenience).
This is an example of a record in the table:
Item{2}
attributes Map{2}
10 Number: 2
11 Number: 4
12 Number: 6
13 Number: 8
id String: YVVVNIL5CB5WXITFTV3JFUBO2IP2C33BY
The numeric fields, such as the "12" field, in the Map can be interpreted as "week10", "week11","week12" and "week13" and the numeric values 2,4,6 and 8 are the number of times the application was launched that week.
What I need to do is get all user ids of the records that have more than 4 launches in a specific week (eg week 12) and I also need to get the list of user ids with a sum of 20 launches in a range of four weeks (eg. from week 10 to 13).
With Dynamoose I have to use the following model:
dynamoose.model(
DYNAMO_DB_TABLE_NAME,
{id: String, attributes: Map},
{useDocumentTypes: true, saveUnknown: true}
);
(to match the table structure generated by the persistence adapter I'm using).
I assume I will need to do DynamoDB "scan" to achieve this rather than a "query" and I tried this to get started and get a records where week 12 equals 6 to no avail (I get an empty set as result):
const filter = {
FilterExpression: 'contains(#attributes, :val)',
ExpressionAttributeNames: {
'#attributes': 'attributes',
},
ExpressionAttributeValues: {
':val': {'12': 6},
},
};
model.scan(filter).all().exec(function (err, result, lastKey) {
console.log('query result: '+ JSON.stringify(result));
});
If you don't know Dynamoose but can help with solving this via the AWS SDK tu run a DynamoDB scan directly that might also be helpful for me.
Thanks!!
Try the following.
const filter = {
FilterExpression: '#attributes.#12 = :val',
ExpressionAttributeNames: {
'#attributes': 'attributes',
'#12': '12'
},
ExpressionAttributeValues: {
':val': 6,
},
};
Sounds like what you are really trying to do is filter the items where attributes.12 = 6. Which is what the query above will do.
Contains can't be used for objects or arrays.
I'm really not sure how to describe what I'm trying to do. I'm trying to create a react-table component where my data is organized in a certain way.
Let's say I have a list of objects like this:
{ id: '887SYEP',
client: 'CS',
side: 'S',
price: 85.8125,
qty: 9866000,
id: '8a59875bdaca5f886c5e7bdc42bb753b78cbe59d' }
Please see the image attached. If "side" prop is "B" then then the price and related data is bid data and if its "S" then its offer data. each object is a stock quote. however i want to order it in such a way that the table looks like this where the highest bids and offers are at the top:
image of ideal table
This data is in one row even though its two separate quote objects. the corresponding "client" and "price" are to the left if its "side" property is type "S" and to the right if its "B" (buy/sell side). is there a way to use one table to achieve this or do i need two? the Bid and Offer prices are only related in so much as its the same stock and a way for the user to see the top prices for each.
first you should filter Buyers and Sellers
let buyers = orders.filter(obj => obj.side === "B")
let sellers = orders.filter(obj => obj.side === "S")
then sort both by price
buyers.sort((a,b) => a.price < b.price)
sellers.sort((a,b) => a.price > b.price)
for simplicity let assume both arrays are of the same length. to combine them do:
let orders = []
for (let index in buyers) {
let {client: BClient, qty: BQty, price: Bid} = buyers[index]
let {client: SClient, qty: SQty, price: Offer} = sellers[index]
orders.push({
BClient,
BQty,
Bid,
Offer,
SQty,
SClient
})
}
then display orders
I am looking for a general solution to a problem with couchdb views.
For example, have a view result like this:
{"total_rows":4,"offset":0,"rows":[
{"id":"1","key":["imported","1"],"value":null},
{"id":"2","key":["imported","2"],"value":null},
{"id":"3","key":["imported","3"],"value":null},
{"id":"4","key":["mapped","4"],"value":null},
{"id":"5,"key":["mapped","5"],"value":null}
]
1) If I want to select only "imported" documents I would use this:
view?startkey=["imported"]&endkey=["imported",{}]
2) If I want to select all imported documents with an higher id then 2:
view?startkey=["imported",2]&endkey=["imported",{}]
3) If I want to select all imported documents with an id between 2 and 4:
view?startkey=["imported",2]&endkey=["imported",4]
My Questtion is: How can I select all Rows with an id between 2 and 4?
You can try to extend the solution above, but prepend keys with a kind of "emit index" flag like this:
map: function (doc) {
emit ([0, doc.number, doc.category]); // direct order
emit ([1, doc.category, doc.number]); // reverse order
}
so you will be able to request them with
view?startkey=[0, 2]&endkey=[0, 4, {}]
or
view?startkey=[1, 'imported', 2]&endkey=[1, 'imported', 4]
But 2 different views will be better anyway.
I ran into the same problem a little while ago so I'll explain my solution. Inside of any map function you can have multiple emit() calls. A map function in your case might look like:
function(doc) {
emit([doc.number, doc.category], null);
emit([doc.category, doc.number], null);
}
You can also use ?include_docs=true to get the documents back from any of your queries. Then your query to get back rows 2 to 4 would be
view?startkey=[2]&endkey=[4,{}]
You can view the rules for sorting at CouchDB View Collation