Introduction to SQL
The SQL, stands for Structured Query Language. It’s a language for interacting with data stored in a relational databases aka RDBMS(Relational Database Management System). SQL allows us to manage or manipulate data within databases.
A database is a collection of tables. And table is a just a set of rows and columns, like Microsoft Office Excel or Google Spreadsheet.
There are many database management system. The few, most popular and widely used are MySQL, SQL Server, Oracle Database and a list goes on.
Big tech giant companies like as Twitter, LinkedIn, Google, Netflix, Airbnb, Facebook, Amazon, etc. all use SQL for back-end data storage and data processing solutions.
With SQL we can perform below actions & more.
- Create, rename, manipulate or drop databases
- Create, rename, manipulate or drop tables in databases
- Execute queries for data retrieval from a tables or tables across databases
- Insert records into tables or tables across databases
- Update records into tables or tables across databases
- Delete records from tables or tables across databases
- Manage stored procedures & views
- Manage permissions on databases, tables, procedures, and views
A relational database is a collection of tables, procedures, views and information that can be related to each other. For example, a table might represent students in a university. SQL is the standard language for interacting with relational databases.
The two formal languages in SQL
- Data Definition Language (DDL)
- DDL is used to manage database operations like create, update, drop, rename of database & tables.
- Data Manipulation Language (DML)
- DML is used for management of data within tables. Operations like selecting, updating, inserting or deleting of data uses DML.
Each row of a table contains information also known as record that represents a single entity.
For example, in an subscribers table, each row represents a single person and this single row is known as record. In table, a field is a column that is represents specific information about every record in the table.
Consider an example, a subscribers table, might have a column containing first and last names for all employees.
The table of subscribers might look like this:
Articles for DDL:
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