Gain insights into SQL by exploring database creation, data manipulation, and advanced queries. Learn about practical applications and practice for SQL interviews to build confidence and readiness.

sql.tar.gz

The ability to work SQL is becoming an increasingly in-demand skill, both for software developers and people in less technical roles. If you’re interested in learning SQL and have no prior experience with it, then this course will be your light in a dark tunnel.

You’ll start by covering the basics of SQL such as how to create a database, how to insert, query, and update data. You’ll also learn fundamental concepts that developers and data scientists use everyday such as multi-table operations, nested queries, and how to set up views. 

Throughout, you’ll get to execute SQL queries in your browser and see results in real-time - you won’t need to worry about set-up.

At the end of this course, you’ll also get some hands-on practice with common SQL interview questions, so when the time comes, you’ll be ready and confident to answer any question that comes your way. Let’s get started!

An Introductory Guide to SQL

# Parameters
A parameter is a placeholder for a variable that is used to pass data to and from a stored procedure. An input parameter is used to pass data value to a stored procedure and an output parameter lets the stored procedure pass a data value back to the caller. A parameter can be defined by specifying the mode as well as the data type and an optional maximum length.

Parameters are used to make a stored procedure flexible. Another reason of using parameters is avoiding direct user inputs in a query string. A user input can result in a runtime error and in worst case a malicious input can potentially harm the system.

In MySQL a parameter can have three modes; __IN__, __OUT__ and __INOUT__. If the mode of a parameter is defined as __IN__, it indicates that the application calling the stored procedure has to pass an argument. The stored procedure can not alter the value of the argument, rather it only works on a copy of the IN parameter and the original value of the parameter is retained after the stored procedure ends. A parameter defined as having __OUT__ mode indicates that the stored procedure will pass an argument back to the caller. The value of an OUT parameter can change in the stored procedure and the new value is passed back in the end. The stored procedure, however, cannot access the initial value of the OUT parameter and its value is NULL when the procedure begins execution. The third mode, __INOUT__ has properties of both the IN and OUT mode. The caller may pass an argument to the stored procedure and the stored procedure can work on it and pass the altered value back to the caller.


## Syntax

> [IN | OUT | INOUT] **parameter_name** **datatype** [(**length**)]

>Connect to the terminal below by clicking in the widget. Once connected, the command line prompt will show up. Enter or copy and paste the command **./DataJek/Lessons/53lesson.sh** and wait for the MySQL prompt to start-up.


This lesson discusses the three different modes of parameters in a stored procedure.

Introduction

Basic SQL

Joins

Nested Queries

Multi Table Operations

Views

Stored Procedures

Triggers

Miscellaneous

Practice & Prep

Epilogue

Parameters

Parameters