Tag: sqls
PreambleMongoDB Conditional operators specify a condition to which the value of the document field shall correspond.Comparison Query Operators $eq (equal)$ne (not equal)$gt (more than)$lt (less...
Many developers, even those who have long been familiar with SQL, do not understand window functions, considering them some kind of special magic for the chosen ones. And although the...
PreambleExternal keys may be set in relational databases when fields from one table refer to fields in another table. You can also set links in MongoDB.Manual link settingThe manual setting of...
PreambleWhen searching for documents in small collections, we won’t have any special problems. However, when collections contain millions of documents, and we need to sample them by a certain...
PreambleIn the previous topics, the collection was created implicitly automatically when the first data were added to it. But we can also create it explicitly by using the db.createCollection(name,...
PreambleThe MongoClient class is used to connect to the mongodb database. It allows you to connect to mongodb (connect method) and disconnect (close method), as well as select the database (selectDB...
Like other database management systems, MongoDB provides an opportunity to update data. The easiest to use method is to save. This method accepts a document as a parameter. Method of saving The...
MongoDB grouping commands: count, group, distinct should be considered separately. Number of items in the collection With the count() function you can get the number of elements in the...
The easiest way to get the database content is to use the find function. The action of this function is largely similar to the usual SELECT * FROM Table query, which extracts all strings. For...
PreambleDatabase plays an important role in every modern web application. Due to the dynamic nature of web applications nowadays, even the simplest applications require some storage, access, and...
PreambleMongoDB has a removal method to remove documents:db.users.remove({name : "Tom"})The remove() method returns the WriteResult object. If one document is deleted successfully, the result is the...
When switching from MS SQL to MySQL, apart from data migration, you must also transfer the application code, which is in the database.Earlier we discussed how to move MS SQL to a MySQL...
MongoDB Database - Having installed the DB, we can now add data to it. All data is stored in the DB in the BSON format, which is close to JSON, so we also need to enter data in this...
When you start working with MongoDB Database, the first thing you need to do is to install the database we need as a current database in order to use it later.To do this, use the use command...
PreambleMongodb compass graphic client: For work with MongoDB, you can use the official graphic client Compass. If you didn’t install MongoDB, Mongo Compass, you can download it by going to...
PreambleThe whole model of the database device in MongoDB can be presented as follows:If in the relational databases the contents are tables, then in the working with databases consists of...