Introduction to SQL

• SQL is standard for Structured Query Language.
• It is a language designed to allow both technical and non-technical users query, manipulate, and transform data from a relational database.
• SQL databases provide safe and scalable storage for millions of websites and mobile applications.
• SQLite, MySQL, Postgres, Oracle and Microsoft SQL Server are popular SQL databases.
• A relational database represents a collection of related (two-dimensional) tables.
• To retrieve data from a SQL database, we need to write SELECT statements, which are often colloquially refered to as queries.
• A query is a statement which declares what data we are looking for, where to find it in the database, and optionally, how to transform it before it is returned.
• Think about database as a table that has columns as properties and rows as instances.
• Select is used to select properties from a table.
• The clause is applied to each row of data by checking specific column values to determine whether it should be included in the results or not.
• You can add a condition using WHERE.
• DISTINCT keyword will blindly remove duplicate rows