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

# ALTER INDEX
It is hard to predict what indexes to create without observing the access patterns for an application. We can add, remove, or modify indexes after the application is deployed. Note that modifying indexes doesn't change the data in the table.


## Example Syntax
> ALTER TABLE **table**
>
> ADD INDEX **indexName (col1, col2, ... coln)**;
>

>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/18lesson.sh** and wait for the MySQL prompt to start-up.

-- The lesson queries are reproduced below for convenient copy/paste into the terminal. 

-- Query 1
ALTER TABLE Actors ADD INDEX nameIndex (FirstName);

-- Query 2
ALTER TABLE Actors ADD INDEX nameIndexWithOnlyTenChars (FirstName(10));

-- Query 3
ALTER TABLE Actors DROP INDEX nameIndex;

-- Query 4
ALTER TABLE Actors DROP PRIMARY KEY;

-- Query 5
CREATE TABLE Movies (Name VARCHAR(100), Released DATE, PRIMARY KEY (Name));
DESC Movies;
ALTER TABLE Movies DROP PRIMARY KEY;
ALTER TABLE Movies ADD PRIMARY KEY (Released);


MySQL allows us to add a new index to an existing table. Say we find out that a lot of users of our application are searching actors by first name. We can speed up their queries by declaring an index on the first name column as follows:

   ```mysql
   ALTER TABLE Actors ADD INDEX nameIndex (FirstName);
   ```


In this lesson we discuss how to modify an index.

Introduction

Basic SQL

Joins

Nested Queries

Multi Table Operations

Views

Stored Procedures

Triggers

Miscellaneous

Practice & Prep

Epilogue

Alter Index

ALTER INDEX

Example Syntax