Reading-Notes
Class 09 summary :
SQL Introduction :
SQL definittion :
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SQL is a standard language for storing, manipulating and retrieving data in databases.
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“Language designed to allow both technical and non-technical users query, manipulate, and transform data from a relational database. And due to its simplicity, SQL databases provide safe and scalable storage for millions of websites and mobile applications”.
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“A relational database is a collection of data items with pre-defined relationships between them. These items are organized as a set of tables with columns and rows”.
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“Tables are used to hold information about the objects to be represented in the database. Each column in a table holds a certain kind of data and a field stores the actual value of an attribute”.
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“The rows in the table represent a collection of related values of one object or entity. Each row in a table could be marked with a unique identifier called a primary key, and rows among multiple tables can be made related using foreign keys”.
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“This data can be accessed in many different ways without reorganizing the database tables themselves”.
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example :
