Sql and Crud

Basics of SQL

• Sometimes referred to as (Structured Query Language) is a programming language designed for managing data in relational database management systems (RDBMS).

• Includes data insert, query, update and delete, schema creation and modification, and data access control.

• The most common operation in SQL is the query, which is performed with the declarative SELECT statement.

o Select retrieves data from one or more tables, or expressions. Standard SELECT statements have no persistent effects on the database.

o Queries allow the user to describe desired data, leaving the database management system (DBMS) responsible for planning, optimizing, and performing the physical operations necessary to produce that result as it chooses.

o A query includes a list of columns to be included in the final result immediately following the SELECT keyword. An asterisk ("*") can also be used to specify that the query should return all columns of the queried tables.

Basics of CRUD

• In computer programming, create, read, update and delete (CRUD) are the four basic functions of persistent storage.

• The acronym CRUD refers to all of the major functions that are implemented in relational database applications, that are considered as a complete application

o Create/Insert - INSERT statement adds one or more records to any single table in a relational database.

o Read(Retrieve)/SELECT - SELECT statement returns a result set of records from one or more tables.

o UPDATE - UPDATE statement changes the data of one or more records in a table.

o Delete(Destroy)/DELETE - statement removes one or more records from a table. A subset may be defined for deletion using a condition, otherwise all records are removed.