querying

问题 The sql tables are as follows: likes with columns drinker and beer, sells with columns bar and beer and frequents with columns drinker and bar. I have previously answered the following statement: "Drinkers who frequent bars which serve some beer they like" with the SQL Query: SELECT DISTINCT y.drinker FROM likes a, sells, frequents y WHERE a.beer = sells.beer AND sells.bar = y.bar AND y.drinker = a.drinker; Now, I am trying to modify the query listed above to answer a similar, yet different

问题 I'm using Elasticsearch v2.3.0. Suppose I have an index with mapping: { "mappings": { "post": { "dynamic": false, "_source": { "enabled": true }, "properties": { "text": { "norms": { "enabled": false }, "fielddata": { "format": "disabled" }, "analyzer": "text_analyzer", "type": "string" }, "subfield": { "properties": { "subsubfield": { "properties": { "subtext": { "index": "no", "analyzer": "text_analyzer", "type": "string", "copy_to": "text" } } } } } }, "_all": { "enabled": false } } } So,

问题 When I run below stored JavaScript function I get errors: > db.system.js.save({_id:"last_n_users", value: function(n){return db.users.find().sort({created_at:-1}).limit(n)}}) > db.eval("last_n_users(10)") Here is the errors: { "value" : "DBQuery: store.users -> undefined" } Why? Please help me? 回答1: The find() function returns a cursor, which can't be returned from JavaScript. The suggested workaround is to use toArray() to get an array return value. Example ... before : > use admin switched

问题 I am having hard time optimizing my SQLAlchemy queries. My SQL knowledge is very basic, and I just can't get the stuff I need from the SQLAlchemy docs. Suppose the following very basic one-to-many relationship: class Parent(Base): __tablename__ = "parents" id = Column(Integer, primary_key = True) children = relationship("Child", backref = "parent") class Child(Base): __tablename__ = "children" id = Column(Integer, primary_key = True) parent_id = Column(Integer, ForeignKey("parents.id"))

问题 I'm trying to query a varbinary column that contain a file (1,2 Gb). I'm using Entity Framework. See below: Database to test CREATE TABLE [dbo].[BIGDATA] ( [id] [bigint] IDENTITY(1,1) NOT NULL, [BIGDATA] [varbinary](max) NULL, CONSTRAINT [PK_BIGDATA] PRIMARY KEY CLUSTERED ([id] ASC) ) ON [PRIMARY] Data to test (any file with 1 Gb) INSERT INTO [dbo].[BIGDATA]([BIGDATA]) VALUES ((SELECT BulkColumn FROM OPENROWSET(BULK N'C:\BigTest.txt', SINGLE_BLOB) AS Document)) Controller to download file

问题 I'm quite new to Firebase and Swift and I'm having some trouble when it comes to querying. So there are basically two things I'd like to do: Query my users and find only those that contain a certain String in their name (or email address) and add them to an array. Get all of my users and add them to an array. The relevant part of my data for this question looks like this: As you can see, I'm using the simplelogin of Firebase (later I'd like too add Facebook login) and I'm storing my users by

问题 I want to load root entities and eager load all it's child collection and aggregate members. Have been trying to use the SetFetchMode in FluentNHibernate, but I am getting duplicates in one of the child collection since I have a depth of 3 levels. DistinctRootEntityResultTransformer unfortunately only removes the root duplications. return Session.CreateInvoiceBaseCriteria(query, archived) .AddOrder(new Order(query.Order, query.OrderType == OrderType.ASC)) .SetFetchMode("States", FetchMode

问题 How can I query the smoothies that have apple in them? (below is a collection with 3 documents) _id => 1 name => 'best smoothie' ingredients => Array ( [0] => apple [1] => raspberry [2] => orange [3] => banana ) _id => 2 name => 'summer smoothie' ingredients => Array ( [0] => lemon [1] => mint ) _id => 3 name => 'yogurt smoothie' ingredients => Array ( [0] => apple [1] => blueberry ) 回答1: If you simply run the below query MongoDB is smart enough to figure out what you're trying to do. {

问题 I am building a notes system on my site and I've got to the stage where users can post notes into the MySQL database using PHP and then PHP prints them out on a page. However, when they print/echo out, the oldest one appears first but I want the most recent first. I also want them to be limited to 10, so only 10 appear on the page. Here is my PHP code, your help will be much appreciated: // initialize some variables $notedisplaylist = ""; $myObject = ""; $result = mysql_query("SELECT * FROM

问题 I have a list of events in my app. A button on the side lets the user add the event date and time to his/her calender. I use a calender intent to redirect the user to the android calender which the corresponding date and time. Now after the user adds the event to his calender, I would like to disable the 'add event' button which corresponds to the events he/she had already added(so the user avoid adding the same event again). How can I do this? I have gone through the new calender API for