I have one model called "Author".It has two attributes.
firstName: {
type: 'string',
unique: true
},
lastName: {
type: 'string',
unique: true
}
So i want to insert an array of author(firstName,lastName).So i used create method to store data.
create: function (req, res) {
let authors = req.body.author_name;
let ids=[],i=0;
Author.create(authors,(err,author)=>{
if(err)res.json('err');
else res.json(author);
});
}
in author_name = [{'abc1','xyz1'},{'abc2','xyz2'}]
it will work fine but after that when i enter
author_name = [{'abc1','xyz1'},{'abc3','xyz3'}]
it wont work.Because i mentioned that both first and last name should be unique.1st data of array is already in database But 2nd argument of array is not in database.So in the end nothing will stored .So i want to store that 2nd argument also.If some of data in array is already in DB then it shloud be ignored and other data should be stored.
So how to do that in better way(not looping if possible)
I think, you need execute find query for the input array, it brings already available records, then you need to exclude them from your input data then try to insert the unique data.
I hope it would help you.
I think you are misunderstanding how your database is functioning. No matter which db technology you are using, an Author object is represented by a single row or record. When you make both firstName and lastName unique fields, that means that first names can never be repeated, and neither can last names. So, for example, you could not have a "Bob Smith" and a "Sara Smith" because that would be repeating a last name.
In the records you are entering in your example, you are not providing a first or last name. It creates a single record with both firstName and lastName empty. Since these fields are unique, you are then not allowed to create any other authors with either first or last names empty.
I think you may need to think about whether you want these fields to be unique, and if storing it via an Author model is really what you want - I had a bit of trouble understanding what you mean by "storing the second argument" but "ignoring the first". Maybe you actually want to just store a list of names, not Author objects?
Related
I'm very much a beginner when it comes to database relationships hence what I suspect is a basic question! I have two database tables as follows:
Projects
id
company_id
name
etc...
rfis
id
project_id (foreign key is id on the Projects table above)
Number (this is the column I need help with - more below)
question
The relationships at the Model level for these tables are as follows:
Project
public function rfi()
{
return $this->hasMany('App\Rfi');
}
RFI
public function project()
{
return $this->belongsTo('App\Project');
}
What I'm trying to achieve
In the RFI table I need a system generated number or essentially a count of RFI's. Where I'm finding the difficulty is that I need the RFI number/count to start again for each project. To clarify, please see the RFI table below which I have manually created with the the 'number' how I would like it displayed (notice it resets for each new project and the count starts from there).
Any assistance would be much appreciated!
Todd
So the number field depends on the number of project_id in the RFI table. It is exactly the number of rows with project_id plus one.
So when you want to insert a new row, you calculate number based on project_id and assign it.
RFI::create([
'project_id' => $project_id,
'number' => RFI::where('project_id', $project_id)->count() + 1,
...
]);
What I understood is that you want to set the value of the "number" field to "1" if it's a new project and "increment" if it's an existing project. And you want to automate this without checking for it every time you save a new row for "RFI" table.
What you need is a mutator. It's basically a method that you will write inside the desired Model class and there you will write your own logic for saving data. Laravel will run that function automatically every time you save something. Here you will learn more about mutators.
Use this method inside the "RFI" model class.
public function setNumberAttribute($value)
{
if(this is new project)
$this->attributes['number'] = 1;
else
$this->attributes['number']++;
}
Bonus topic: while talking about mutators, there's also another type of method called accessor. It does the same thing as mutators do, but just the opposite. Mutators get called while saving data, accessors get called while fetching data.
I have a file object store by indexing name and library_id like below,
let objectStore = db.createObjectStore('file', { keyPath: 'id' });
tempStore.createIndex('nameLibId', ['attributes.name', 'attributes.library_id'], { unique: false });
The object store contains multiple library id's files. I'd like apply the name sort to the particular library id's files. I tried indexing in the below format but it returns empty data.
let self = this,
db = get(self, 'db'),
transaction = db.transaction(["file"], "readonly"),
objectStore = transaction.objectStore("file"),
index = objectStore.index('nameLibId'),
keyRange = IDBKeyRange.only('library_id')),
req = index.getAll(keyRange);
req.onsuccess = ((e)=>{
console.log(e.target.result); // returns empty array
});
Attached the screenshot of db model for reference.
24536475, abc, created, jhgf and lastmodified file names are belongs to a library id called 123.
Screen Shot..* file names are belongs to an another library id called 234.
I need the files which are sorted by name only the given library id. Any help would be highly appreciated.
If your index is based on a properties array and you want to match something using IDBKeyRange.only, then your parameter to IDBKeyRange.only should also be an array. Right now you are comparing a basic string value against a properties array value, where of course nothing matches. In other words, you cannot query against a two-part array using only one part of it.
Furthermore, the parameter to IDBKeyRange.only isn't a property name, it is a value. You want to specify a value to match in the index's set of keypath values. For example, if your index was based exclusively on attributes.name, then you would want to specify a particular value within that index, such as "abc".
And so, taking into account the above two points, and given that your index is not a single value but is instead an array of two properties, you need to revise your parameter to IDBKeyRange.only to look for an array. Something like IDBKeyRange.only(['abc', 'yoktc....']);.
Now, this is further complicated by the fact that what you are doing in your code does not actually accomplish what you want. Ignoring the sort concern for a moment, you only want to use the id condition, and not the name, when matching rows of this index. So you might be tempted to try IDBKeyRange.only([undefined, 'asdf']). Unfortunately this will not work at all because you cannot specify undefined (you will get a javascript error).
So, you must always query by both values, even though you only want to apply criteria to one of the values. The trick here is that you switch to using a different method than only. You use IDBKeyRange.bound(), and furthermore, you do a trick where you specify a criteria such as "smallest possible number is less than my number and my number is less than largest possible number", e.g. a condition that always is true. You use "smallest possible value" as your lower boundary, and "largest possible value" as your upper boundary.
Here is an example in your case. The smallest possible value of name I think is empty string. The largest possible value of name is probably any non-alphanumeric character, so let's use tilde "~". So, now we would rewrite the range parameter. Instead of using IDBKeyRange.only, we use IDBKeyRange.bound. It looks like the following (roughly):
var libId = ???;
var smallestNameValue = '';
var largestNameValue = '~';
var lowerBound = [smallestNameValue, libId];
var upperBOund = [largestNameValue, libId];
var range = IDBKeyRange.bound(lowerBound, upperBound);
Now, the second part, regarding sorting, and a major caveat of using indices that have multiple parts (not to be confused with the multiPart index property, ugh). And I myself get this backwards all the time, so I might even be wrong here and the above will work. The problem with the above is that one the first criterion is met the second is ignored, because of how the short-circuited array sorting algorithm works in indexedDB's comparison function. Your query is going to match everything, because every index row meets the criteria. So the trick to this is to always query first by the important condition, to basically pay attention to the order in which you specify your conditions. So what that means is that you need to switch the order of the properties you specified when creating the index, so that you can query first by libId and then by name.
Instead of createIndex('nameLibId',['attributes.name','attributes.library_id']); you want to do createIndex('nameLibId',['attributes.library_id', 'attributes.name']);. And this also means you need to swap your lower and upper bound queries, e.g. var lowerBound = [libId, smallestNameValue]; (and don't forget to switch the upper).
As I mentioned in my answer on using compound indices, you can always using indexedDB.cmp to experiment. Right now, open up the console on this web page. In the console, type something like this:
indexedDB.cmp(['', '5'], ['~', '5']);
Take a look at the results.
Some final notes:
Tilde might be the wrong thing to use, sorry but I am not bothering to remember, you could also just try any valid sentinel value, where by sentinel I mean any value you know will always come after all your other valid values
As I point out in my other answer, if either prop is missing in the data the actual object won't match
for cmp, -1 means left is less than right, 0 means left equals right, and 1 means left greater than right
As part of a tool I am creating for my team I am connecting to an internal web service via PowerQuery.
The web service returns nested JSON, and I have trouble parsing the JSON data to the format I am looking for. Specifically, I have a problem with extracting the content of records in a column to a comma separated list.
The data
As you can see, the data contains details related to a specific "race" (race_id). What I want to focus on is the information in the driver_codes which is a List of Records. The amount of records varies from 0 to 4 and each record is structured as id: 50000 (50000 could be any 5 digit number). So it could be:
id: 10000
id: 20000
id: 30000
As requested, an example snippet of the raw JSON:
<race>
<race_id>ABC123445</race_id>
<begin_time>2018-03-23T00:00:00Z</begin_time>
<vehicle_id>gokart_11</vehicle_id>
<driver_code>
<id>90200</id>
</driver_code>
<driver_code>
<id>90500</id>
</driver_code>
</race>
I want it to be structured as:
10000,20000,30000
The problem
When I choose "Extract values" on the column with the list, then I get the following message:
Expression.Error: We cannot convert a value of type Record to type
Text.
If I instead choose "Expand to new rows", then duplicate rows are created for each unique driver code. I now have several rows per unique race_id, but what I wanted was one row per unique race_id and a concatenated list of driver codes.
What I have tried
I have tried grouping the data by the race_id, but the operations allowed when grouping data do not include concatenating rows.
I have also tried unpivoting the column, but that leaves me with the same problem: I still get multiple rows.
I have googled (and Stack Overflowed) this issue extensively without luck. It might be that I am using the wrong keywords, however, so I apologize if a duplicate exists.
UPDATE: What I have tried based on the answers so far
I tried Alexis Olson's excellent and very detailed method, but I end up with the following error:
Expression.Error: We cannot convert the value "id" to type Number. Details:
Value=id
Type=Type
The error comes from using either of these lines of M code (one with a List.Transform and one without):
= Table.Group(#"Renamed Columns", {"race_id", "begin_time", "vehicle_id"},
{{"DriverCodes", each Text.Combine([driver_code][id], ","), type text}})
= Table.Group(#"Renamed Columns", {"race_id", "begin_time", "vehicle_id"},
{{"DriverCodes", each Text.Combine(List.Transform([driver_code][id], each Number.ToText(_)), ","), type text}})
NB: if I do not write [driver_code][id] but only [id] then I get another error saying that column [id] does not exist.
Here's the JSON equivalent to the XML example you gave:
{"race": {
"race_id": "ABC123445",
"begin_time": "2018-03-23T00:00:00Z",
"vehicle_id": "gokart_11",
"driver_code": [
{ "id": "90200" },
{ "id": "90500" }
]}}
If you load this into the query editor, convert it to a table, and expand out the Value record, you'll have a table that looks like this:
At this point, choose Expand to New Rows, and then expand the id column so that your table looks like this:
At this point, you can apply the trick #mccard suggested. Group by the first columns and aggregate over the last using, say, max.
This last step produces M code like this:
= Table.Group(#"Expanded driver_code1",
{"Name", "race_id", "begin_time", "vehicle_id"},
{{"id", each List.Max([id]), type text}})
Instead of this, you want to replace List.Max with Text.Combine as follows:
= Table.Group(#"Changed Type",
{"Name", "race_id", "begin_time", "vehicle_id"},
{{"id", each Text.Combine([id], ","), type text}})
Note that if your id column is not in the text format, then this will throw an error. To fix this, insert a step before you group rows using Transform Tab > Data Type: Text to convert the type. Another options is to use List.Transform inside your Text.Combine like this:
Text.Combine(List.Transform([id], each Number.ToText(_)), ",")
Either way, you should end up with this:
An approach would be to use the Advanced Editor and change the operation done when grouping the data directly there in the code.
First, create the grouping using one of the operations available in the menu. For instance, create a column"Sum" using the Sum operation. It will give an error, but we should get the starting code to work on.
Then, open the Advanced Editor and find the code corresponding to the operation. It should be something like:
{{"Sum", each List.Sum([driver_codes]), type text}}
Change it to:
{{"driver_codes", each Text.Combine([driver_codes], ","), type text}}
I have a sequelize model that uses mysql functions to create guid such as:
guid: {
type: DataTypes.STRING.BINARY,
defaultValue: sequelize.fn('UuidToBin', sequelize.fn('uuid')),
primaryKey: true
},
inProcess: DataTypes.BOOLEAN,
...
I successfully create new records including a binary guid using the create method,
MessagesDBModel.create(messageObj)
.then((savedMessage) => res.send(200, {
status: 200,
message: "OK",
guid: savedMessage.guid.toString('hex') //outputs [object Object]
But, the value of guid cannot be retrieved from the savedMessage object. When I set a breakpoint, savedMessage.dataValues.guid = Fn.
How can I access the inserted value of guid instead of the function that created it?
You can think of it in the case of build first. In the code below
const record = Model.build({}) // assuming Model has guid attribute that you wrote
What should be record.guid at this point? Since the transaction has not yet occurred, the function should not be executed and therefore the guid value can not be determined.
This is not a problem for scalar values that have the same value before and after the transaction completes. However, in the case of function, since the point at which the value is determined is the point at which the transaction is committed, sequelize has to replace the values of entire objects included in the transaction with the execution result of the function. It seems to be a very hard work.
Currently, it seems like a good way to select again with last_inserted_id or something like that.
I ended up taking a different approach. I created a stored procedure. Within the procedure declared #guid using the MySQL function. Inserted to all the appropriate tables, then selected back the #guid value for further use in the application.
I'm trying to create a database (json) with Firebase.
I searched the docs and the net but couldn't find a clear way to start.
I want to have a database of users.
each user (represented as UID) should have a nickname and a list of friends.
I tried making a .json file that looks like this:
{
users:{
}
}
and adding it to the Firebase console to get started but it wouldn't work.
How can I do it?
the database should look like this:
{
users:{
UID:{
nickname: hello
friends: UID2
}
UID2:{
nickname: world
friends: UID
}
}
I don't know if I got that right, so I would really appreciate any help you guys could give me at this subject.
Thanks in advance!
Seems like a good place to start. I would make two changes though.
keep the list is friends separate
keep the friends as a set, instead of a single value or array
keep the list is friends separate
A basic recommendation when using the Firebase Database is to keep your data structure shallow/flat. There are many reasons for this, and you have at least two.
With your current data structure, say that you want to show a list of user names. You can only get that list by listening to /users. And that means you don't just get the user name for each user, but also their list of friends. Chances that you're going to show all that data to the user are minimal, so that means that you've just wasted some of their bandwidth.
Say that you want to allow everyone to read the list of user names. But you only want each user to be able to read their own list of friends. Your current data structure makes that hard, since permission cascades and rules are not filters.
A better structure is to keep the list of user profiles (currently just their name) separate from the list of friends for each user.
keep the friends as a set
You current have just a single value for the friends property. As you start building the app you will need to store multiple friends. The most common is to then store an array or list of UIDS:
[ UID1, UID2, UID3 ]
Or
{
"-K.......1": "UID1"
"-K.......5": "UID2"
"-K.......9": "UID3"
}
These are unfortunately the wrong type for this data structure. Both the array and the second collection are lists: an ordered collection of (potentially) non-unique values. But a collection of friends doesn't have to be ordered, it has to be unique. I'm either in the collection or I'm not in there, I can't be in there multiple times and the order typically doesn't matter. That's why you often end up looking for friends.contains("UID1") or ref.orderByValue().equalTo("UID1") operations with the above models.
A much better model is to store the data as a set. A set is a collection of unordered values, which have to be unique. Perfect for a collection of friends. To store that in Firebase, we use the UID as the key of the collection. And since we can't store a key without a value, we use true as the dummy value.
So this leads to this data model:
{
users:{
UID:{
nickname: hello
}
UID2:{
nickname: world
}
}
friends:{
UID:{
UID2: true
}
UID2:{
UID: true
}
}
}
There is a lot more to say/learn about NoSQL data modeling in general and Firebase specifically. To learn about that, I recommend reading NoSQL data modeling and watching Firebase for SQL developers.
I keep a collection of Friends where the users field is an array of 2 user ids: ['user1', 'user2'].
Getting the friends of a user is easy:
friendsCollection.where("users", "array-contains", "user1").get()
This should get you all documents where user1 appears.
Now the tricky part was on how to query a single friend. Ideally, firebase would support multiple values in array-contains, but they won't do that: https://github.com/firebase/firebase-js-sdk/issues/1169
So they way I get around this is to normalize the users list before adding the document. Basically I'm utilizing JS' truthiness to check what userId is greater, and which is smaller, and then making a list in that order.
when adding a friend:
const user1 = sentBy > sentTo ? sentBy : sentTo
const user2 = sentBy > sentTo ? sentTo : sentBy
const friends = { users: [user1, user2] }
await friendsCollection.add(friends)
This basically ensures that whoever is part of the friendship will always be listed in the same order, so when querying, you can just:
await friendsCollection.where("users", "==", [user1, user2]).get()
This obviously only works because I trust the list will always have 2 items, and trust that the JS truthiness will work deterministically, but it's a great solution for this specific problem.