Tag: sql server
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...
What is PostgreSQL array? In PostgreSQL we can define a column as an array of valid data types. The data type can be built-in, custom or enumerated. In addition, arrays play an important...
PreambleMost Linux distributions come with MySQL.If you want to use MySQL, my recommendation is that you download the latest version of MySQL and install it yourself. Later you can update it to...
PreambleStarting with Microsoft SQL Server 2008, by default, the group of local administrators is no longer added to SQL Server administrators during the installation, this can only be done...
PreambleYou can use the LEN function () to find the length of a string value in SQL Server, for example, LEN (emp_name) will give you the length stored in the emp_name string. Remember that...
PreambleIn this article, you will learn how to query today’s date data in MySQL using the built-in date functions.Getting today's date in MySQL using built-in date functionsSometimes you may...
In this article, there are 8 concepts to understand if you want to become an advanced programmer faster. The list is not complete, but it can be a good starting point for self-education in...
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...