Databases in SQL (Part -2)

Data usually comes through raw format in an unorganized manner and processing of such data is called ‘Information’.

Our Data are stored in Databases [db] consists set of Tables (Rows & Columns). A Table is an organized collection of data stored in the form of Rows and Columns. Columns can be categorized as vertical, while Rows as horizontal. The Columns in a table are called Fields in records while the Rows can be referred to as unique Records.

For example, a Table that contains Employee data for a company might contain a row for each employee and columns representing employee information such as employee number, name, address, job title, etc.

A Computer can have one or more than one instance of SQL Server installed. Each instance of SQL Server can contain one or many databases. Within a database, there are one or many object ownership groups called schemas. Within each schema there are database objects such as tables, views, and stored procedures. Some objects such as certificates and asymmetric keys are contained within the database, but are not contained within a schema.

SQL Server databases are stored in the file system in files. Files can be grouped into file-groups. 

At a minimum, every SQL Server database has two operating system files: a data file and a log file. Data files contain data and objects such as tables, indexes, stored procedures, and views. Log files contain the information that is required to recover all transactions in the database. Data files can be grouped together in file-groups for allocation and administration purposes.

The number of tables in a database is limited only by the number of objects allowed in a database (2,147,483,647). A standard user-defined table can have up to 1,024 columns. The number of rows in the table is limited only by the storage capacity of the server.

SQL vs MySQL: Key Difference (Part -1)

SQL extends for Structured Query Language that enables the user to design and manage databases, while MySQL is a Relational database management system that allows a user to store and retrieve data from the database.

SQL is a standard language for retrieving and manipulating structured databases. On the contrary, MySQL is a relational database management system, like SQL Server, Oracle or IBM DB2, that is used to manage SQL databases.

Both the technologies work on the concept of storing data as per schema (table storage). MySQL is inclined more towards selecting the data to facilitate data display, update and save the data again. It is a bit weaker than SQL Server in terms of data insertion and deletion.

Many famous web-based applications and companies use MySQL like WordPress, YouTube, Joomla, etc. SQL is also used by many platforms like MYSQL, Oracle, Microsoft SQL Server, etc.

Access Modifiers in Scala (Class -38)

Access Modifiers in scala are used to define the access field of members of packages, classes or objects in scala. For using an access modifier, you must include its keyword in the definition of members of package, class or object. These modifiers will restrict accesses to the members to specific regions of code.

There are 3 types of Access Modifiers in Scala:

a)      Public

b)      Private

c)       Protected

Singleton Object in Scala (Class -37)

Singleton Object is another Class of only One instance which can be created using keyword called ‘object’. An object that can exist without a class is a singleton object. It objects keyword is used to define it.

 A Scala object is a singleton object that is accessible to any Scala code that has visibility of that object definition. The term singleton here refers to the fact that there is a single instance of the object definition within the virtual machine executing the Scala program. This is guaranteed by the language itself and does not require any additional programmer intervention.

Objects can • extend classes, • mix in traits, • define methods and functions • as well as properties (both vals and vars). • But they cannot define constructors.

Class and Objects in Scala (Class -36)

 Class is nothing but blueprint for creating an object.

         e.g.:- variables, function objects, methods, etc.

 A Class is one of the basic building blocks of Scala. Classes act as templates which are used to construct instances. Classes allow programmers to specify the structure of an instance (i.e. its instance variables or fields) and the behaviour of an instance (i.e. its methods and functions) separately from the instance itself. This is important, as it would be extremely time-consuming (as well as inefficient) for programmers to define each instance individually. Instead, they define classes and create instances of those classes.