nested-queries

问题 So I know that in mongodb, I can get all values and then iterate through them but I was wondering if in mongodb there is an option to get only a certain field. So for example suppose my collection is structured as follows: {_id: { field1,field2,field3} } {description: { field1,field2,field3, data:{ field1,field2,field3 } } } {otherdata: {field1,field2,field3} } Now, I need the value of description.data.field1 so any suggestions on how to do that? So far I have tried using following commands:

问题 I am trying to filter list of maps from a dynamodb table which is of the following format. { id: "Number", users: { { userEmail: abc@gmail.com, age:"23" }, { userEmail: de@gmail.com, age:"41" } } } I need to get the data of the user with userEmail as "abc@gmail.com". Currently I am doing it using the following dynamodb query. Is there any another efficient way to solve this issue ? var params = { TableName: 'users', Key:{ 'id': id } }; var docClient = new AWS.DynamoDB.DocumentClient();

问题 I need to find the distinct drinkers that ordered 'VODKA' and 'WHISKY'. I AM ONLY ALLOWED TO USE A NESTED QUERY. No other format is accepted. I am quite new to sql so any help would be greatly appreciated! Here are the tables I am trying to retrieve data from: CREATE TABLE DRINKERS ( /* All drinkers */ DRINKER VARCHAR(30) NOT NULL, CONSTRAINT DRINKERS_PKEY PRIMARY KEY (DRINKER)); CREATE TABLE ORDERS( /* Drinkers visit pubs and consumes drinks */ DRINKER VARCHAR(30) NOT NULL, /* Drinker name *

问题 I have a recipe entity which have some tags (many to many mapping) and I want to search recipes by tags. Here's my Recipe entity: /** * @ORM\Entity * @ORM\Table(name="recipes") * @ORM\HasLifecycleCallbacks * @ExclusionPolicy("all") */ class Recipe { /** * @ORM\Id * @ORM\Column(type="integer") * @ORM\GeneratedValue(strategy="AUTO") * @Expose */ protected $id; /** * @ORM\Column(type="string", length=150) * @Expose */ protected $name; ... /** * @ORM\ManyToMany(targetEntity="RecipesTag",

问题 Is it always a best practice to use - Select E.Id,D.DeptName from Employee E join Dept D on E.DeptId=D.Id instead of - Select Employee.Id,Dept.DeptName from Employee join Dept on Employee.DeptId=Dept.Id Other than readability and reducing length of the query what are benefits of using aliases ? When I consulted with our Database expert he says query may break if there are no aliases at times...which I dont understand completely...I would appreciate if anyone would share their thoughts and

问题 I have a query for example Query1 = Select Name from table where some Criteria . Now this query returns a result set of course, what I want is to query the result set of this query, for example I only want the unique Names from the above query select Distinct(Name) from Query1 . I should mention that I know I can just use distinct in Query1 but this is just an example my real scenario is somewhat different, what I want to know is whether it's possible to query the result set of a previous

问题 I have a query for example Query1 = Select Name from table where some Criteria . Now this query returns a result set of course, what I want is to query the result set of this query, for example I only want the unique Names from the above query select Distinct(Name) from Query1 . I should mention that I know I can just use distinct in Query1 but this is just an example my real scenario is somewhat different, what I want to know is whether it's possible to query the result set of a previous

问题 I have problem with nested query. In query5.whereEqualTo("piwo", followList2.get(0)) I want to get the object, but it spits error that followList2 needs to be declared final, but when it does all the anonymous class gets in red with Cannot resolve constructor(...) error. Anyone got this before? ParseQuery<ParseObject> query3 = ParseQuery.getQuery("Piwo"); query3.whereEqualTo("marka", beer); // TODO if(beer == "all") then don't use it query3.findInBackground(new FindCallback<ParseObject>() {

问题 Have a table users and there is a field invited_by_id showing user id of the person who invited this user. Need to make a MySQL query returning rows with all the fields from users plus a invites_count field showing how many people were invited by each user. Something like this: SELECT User.*, Count.count FROM users AS User, ( SELECT COUNT(*) AS count FROM users WHERE users.invited_by_id=User.id ) AS Count; This one is not working so I need a working one. 回答1: SELECT u.*, ( SELECT COUNT(*)

问题 I'm trying to understand solr nested queries but I'm having a problem undestading the syntax. I have the following two indexed documents (among others): <doc> <str name="city">Guarulhos</str> <str name="name">Fulano Silva</str> </doc> <doc> <str name="city">Fortaleza</str> <str name="name">Fulano Cardoso Silva</str> </doc> If I query for q="Fulano Silva"~2&defType=edismax&qf=name&fl=score I have: <doc> <float name="score">28.038431</float> <str name="city">Guarulhos</str> <str name="name"