Отличия между движками MyISAM и InnoDB простым языком.
Differences PRIMARY KEY VS UNIQUE in MySQL
So what's different from the PRIMARY KEY and UNIQUE CONSTRAINT?
1. PRIMARY KEY does not allow NULL in their fields, and UNIQUE - allow.
2. PK - there can be only one. UQ - can be any number.
3. When you create a PRIMARY KEY by default creates a clustered index, and when you create a UNIQUE not.
CRUD MySQL in PHP
CRUD — (create read update delete) abbreviation naming four basic functions for working with databases - create, read, update and delete.
The classic application to work with the database is usually called CRUD - on the first letter of standard operations, Create, read, update and delete.
It's like the notes in music - any application consists of these basic elements. In our case it is a PHP web page that displays a list of records in the database as a list of (R), allows you to add new records in the MySQL database (C), edit them (U) and delete (D) from database.
With the help of this php application class is implemented through a few stitches.
Here they are:
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