MySQL Foreign Key Referential Actions

Referential Actions When an UPDATE or DELETE operation affects a key value in the parent table that has matching rows in the child table, the result depends on the referential action specified by ON UPDATE and ON DELETE subclauses of the FOREIGN KEY clause. Referential actions include: CASCADE: Delete or update the row from the parent table and automatically delete or update the matching rows in the…

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Bash: Reading Input

The read command is a builtin command that reads from the standard input. By default, it reads until a newline is received. The input is stored in one or more variables given as arguments: read var If more than one variable is given, the first word (the input up to the first space or tab)…

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Bash: Printf

printf: formatting and printing data printf FORMAT ARG … The FORMAT string can contain ordinary characters, escape sequences, and format specifiers. Ordinary characters are printed unchanged to the standard output. Escape sequences are converted to the characters they represent. Format specifiers are replaced with arguments from the command line. Escape sequences are single letters preceded…

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Let’s Discover Microsoft Access

Microsoft Access is a Database Management System (DBMS) from Microsoft that combines the relational Microsoft Jet Database Engine with a graphical user interface and software-development tools. It is a member of the Microsoft Office suite of applications, included in the professional and higher editions. MS Access Objects MS Access uses “objects” to help the user…

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Some of The Most Important SQL Commands

SELECT – extracts data from a database UPDATE – updates data in a database DELETE – deletes data from a database INSERT INTO – inserts new data into a database CREATE DATABASE – creates a new database ALTER DATABASE – modifies a database CREATE TABLE – creates a new table ALTER TABLE – modifies a table DROP TABLE – deletes a table CREATE INDEX –…

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