All You Need to Know About SQL: SQL Tutorial for Beginners & Experienced

Introduction

A SQL Tutorial guide can help you in learning SQL basics which would, in turn, help you in becoming an expert SQL developer. You will get a detailed idea of what is Structured Query Language and how to deploy SQL to work with the relational database management system. Basically, Structured Query Language is used to work with a relational database and store, retrieve, and manipulate data stored in relational databases.

SQL Tutorial for Beginners and SQL Server Tutorial For Experienced

In this blog for “SQL Tutorial Guide for Beginners,” you will learn SQL commands, syntax, data types, working with tables & queries, etc. To know more in detail what exactly SQL contains, you should download the syllabus first.

This blog is suitable for college students who want to learn SQL from the basics. It is beneficial for software developers, architects, database administrators, and managers who want to take the first step to learn SQL to excel in their careers. There are no prerequisites to learn SQL, but a basic understanding of databases or computer languages can be beneficial. You can join an online SQL training program from JanBask Training for ultimate growth and achievement.

SQL Tutorial Guide for Beginners and SQL server tutorial for experienced

What is a Table in SQL?

Tables are used to store data and information in SQL Server. Every table in SQL is stored with a unique name and composed of rows and columns. Moving ahead, you need to define a data type to store information in a table.  If you want to use tables for your database application, you should know how to create it and add data to the table. The CREATE TABLE keyword is used to create a table in the SQL. Its basic syntax can be given as below.

CREATE TABLE new_table_name ( First_column first_column_data_type, Second_column second_column_data_type, Third_column third_column_data_type, --- Last_column last_column_data_type );

Here, you have to focus on three major categories, when creating a table for the first time.

• You should not be able to enter Not Null values in the table.
• You cannot use duplicate values, so put a UNIQUE keyword in between.
• Define a primary key for the column that is Unique and Not Null. We will be discussing the primary key in SQL in detail later.

SQL Server Tutorial For Experienced: What is a primary key in SQL?

A primary key is a special column within a SQL table that is used to identify records uniquely. Every time you are creating a table in SQL, you should add a primary key first. Also, don’t forget to add primary key constraints to make the concept a little more meaningful. When multiple primary keys are defined for a table, it is named as the composite primary key.

The objective of using a primary key is to enhance performance and storage. If you are using multiple columns as the primary key, then you require more storage in that case. When we are talking about performance, primary key addition generally results in enhanced performance standards.

A Primary key is a critical component in SQL database systems, and you can use the foreign key in the absence of a primary key. Every SQL developer has to deal with a primary key during their work experiences. The real-life examples of primary keys are Roll numbers in schools or colleges, Aadhar card numbers, employee ID, etc. Adding a primary key is easy in an SQL server. Here is the syntax for your reference.

CREATE TABLE Column1 data_type[(size)] NOT NULL PRIMARY KEY, COLUMN2 data_type [(size)], ….);

To know more on the primary key, its features, and technical advantages, Click Here.

SQL Server Tutorial For Experienced: SQL Data Types

When you create a table in SQL, you want to store data as well. For this purpose, you need Data types. It has to be defined for each entry in the SQL table. For example, if you want to store the numeric data, then “int” data type can be used. If you want to store the character data, then “char” data type can be used. In this way, there are plenty of data types available in the SQL as per the requirement.  They are divided into five major categories as given below.

1. Exact Numeric Data Types
2. Approximate Numeric data types
3. Character String data types
4. Date and Time Datatypes
5. Binary Data Types
6. Unicode Character String data types
7. Miscellaneous Data types

All these data types have different ranges and rules for using them. To get a detailed idea of Data types in SQL, click here.

SQL Server Tutorial For Experienced: Different Types of Joins in SQL

A SQL Join is used to merge data from different sources or tables. SQL database is used to manage data or information in the form of tables. It is necessary to define a clear relationship among different tables and datasets to perform an action. These relations are defined with the help of joins in SQL. They are divided into two major categories: Inner Joins and Outer Joins.

An inner join in SQL is used to return results from two different tables. Rows are combined generally based on the requirements. Here is the Venn Diagram representation of the Inner Join in SQL:

An Outer Join returns the rows that are not common in both the table and an inner join returns the common rows in both the tables. So, the output will be different here when compared to the result of the inner join. An outer join is further divided into three broad categories:

• Left Outer Join
• Right outer join
• Full Outer Join

Null values are also taken as the part of inner and outer joins as no value is present sometimes in columns. In the case of a left outer join, all the data in the left side is returned as the outcome. Similarly, in the case of the right outer join, all the data on the right side is returned as the outcome. Full outer join is used to combine the whole data from two tables, whether it is common or not. To know about SQL Joins in detail with examples, Click Here.

SQL Server Tutorial For Experienced: What is a Foreign key in SQL?

A foreign key is used to establish a relationship among different tables, and it explains to you how data is related among multiple tables. The major benefit of using a foreign key in SQL is Data Integrity, and it avoids notifications that could violate the data integrity rules.

A Foreign key is as important as a primary key, and it holds the capability to manage data updates in interesting ways. It is used to refer to the primary key of another table and helps in maintaining links among tables. In the case of a complex database system, it is necessary to maintain a healthy relationship among tables logically, and it can be done gracefully with the help of foreign keys. To go a little deeper into the concept, Click Here.

Keep in mind that using foreign keys is not as easy as primary keys. You have to put extra effort to know how can you use the Foreign key for your database tables. The best idea is to learn the implementation of different keys in SQL practically. For this purpose, take a SQL certification course from JanBask Training now and start learning practical aspects of SQL right away. Before you enroll in the final program, take a demo class first to get an idea of the online learning environment at JanBask Training.

What is a Candidate Key in SQL?

Keys can be defined as a set of attributes that are generally required for accessing tuples from a database table. They are used to construct relationships among two tables and work similarly to a primary key. The major difference is that the primary key can be single, and candidate keys are generally multiple.

In usual practice, keys are needed to improve the overall performance of a database, so they should be selected wisely. A wrong selection of keys may have an adverse impact on database performance. A candidate key can qualify as a primary tool, but it should be Unique and Not Null for this purpose.

When you start working with databases, you will realize that primary keys change seldom. When all candidate keys qualify to become a candidate key, here an experienced DBA should decide which can be used as the primary key in that case. It is not possible to establish a relationship without a candidate key.

To know more about a candidate key in SQL and how it is different from the primary key, Click Here.

What is a Composite Key in SQL?

Keys are the vital components to set up a connection among different database tables. There are a few imperative keys in SQL like primary key, candidate key, foreign key, or composite key, etc. We have already discussed the primary key, candidate key, foreign key in the earlier section. Here, we will be discussing a composite key in SQL and why it is significant for database applications.

A composite key is used to combine at least two columns in the table that are utilized to remarkably recognize each row in a table. It makes sure that column data is unique before they are consolidated. In a few cases, the composite key can qualify as a primary key too based on the arrangement of sections.

To know more about a composite key in SQL and how it is different from the primary key and the Foreign key, Click Here.

SQL Command Cheat Sheet

An SQL commands cheat sheet gives you a complete idea of popular SQL commands that can be used with your database to improve its performance incredibly. When all commands are available in a single place, they can be used quickly without wasting time. They can be divided into different categories further as DDL commands, DCL commands, DML commands, etc. Once you go through the SQL command cheat sheet, it can be used to perform different operations in different situations.

Tips for using SQL command Cheat Sheet

• It can be used with an IDE or tool where users are trying to connect with the database.
• It can be used to connect with different databases and manage complex data operations.
• It uses a set of aggregate functions use along with an SQL cheat sheet and performing complex data operations based on the data query.
• It helps you in managing Views, Triggers, and Indexes, etc.
• It includes a set of logical and comparison operators to execute a query.
• It includes a complete set of data types (more than 40 in SQL) that are used to store data in a database using different formats like numeric, characters, strings, floats, etc.

Complex Queries in SQL

We have already discussed what a query in SQL is. This is the time to discuss the complex SQL queries and when they are used. A query becomes complex when it is using multiple joins, multiple nested conditions, multiple comparison or logical operators, multiple operators to act. It is generally difficult to understand how we should use different SQL concepts together.

For writing a complex SQL query in SQL, you should consider the following facts:

• Focus on database relationships; how are tables connected together.
• Focus on the outcome, what you need to compute finally.
• You should know how to break queries into manageable parts.
• You should know how to aggregate the result sets.
• Write a query that is easy to read and understand.
• You should know how to debug a query.

For debugging a complex SQL query in SQL, you should consider the following facts:

• Check the syntax and logic
• Check the SQL joins
• Check attributes
• Check predicates
• Check nested queries, and more.

It is good to write simple queries in SQL instead of complex SQL queries; otherwise, it may confuse readers and developers both. Here, we have given a brief idea of complex SQL queries. To know these queries in detail and why you should avoid them, Click Here.

What is a subquery in SQL?

A subquery is a nested or inner query in SQL within another SQL query, and it is embedded with the where clause to process the final outcome. SQL subqueries are generally used with comparison operators and SELECT, DELETE, INSERT, and UPDATE statements. A subquery is usually composed of a single column and enclosed within parentheses. It can be used with the Group By clause, but it should not be used with the Order By clause. It can be used to return multiple rows together with the “IN” operator. It cannot be enclosed quickly within a set function. The basic syntax of a SQL subquery is given below.

SELECT column_name [, column_name ] FROM table1[, table2 ] WHERE column_name OPERATOR (SELECT column_name [, column_name ] FROM table1 [, table2 ] [WHERE])

It is possible to join subqueries in SQL if required. When subqueries are joined together, the final outcome is not so stringent, so it is better to use the Where clause in that case. You must be wondering where you should use a subquery. It can be used to enhance the overall performance of queries when used appropriately.

What is a LIKE operator in SQL?

It is a logical operator to check if a specified string matches the desired pattern or not. A pattern is made up of regular expressions or wild characters, etc. It can be used with different SQL statements like DELETE, WHERE, SELECT, UPDATE, etc. It is used to filter rows based on matching patterns. Here is the basic syntax of a LIKE operator in SQL for your reference:

Column | expression LIKE pattern [ESCAPE escape_character]

Let us understand the concept with a real-life example. Consider you are available with a specific portion of the address then how to fetch the complete one. You can use the LIKE operator in this situation to filter addresses and fetch the desired output. It is clear from the discussion that the SQL LIKE operator is a wonderful searching technique when we are not sure what we are looking for exactly. TO learn LIKE operators in SQL with examples, click here.

SQL Formatter

Would you like to read a length of plain code? No one would like actually. When writing a detailed SQL script, there is a lot of unformatted SQL code that is tough to understand. Here you should use a SQL formatter with fabulous formatting options to make things easier for you. A formatted SQL script is easy to read consistently.

If you are performing formatting manually, then it can be a time-consuming process. The best idea is to use formatting tools to accelerate the process and make it more efficient for developers as well. One of the popular options in SQL formatting includes Indenting. It is used to align the content at the right space in a consistent manner. If you want to know how you can use a SQL formatter to manage the highly complex code, then Click Here.

Top 100 SQL Interview Questions & Answers

The increased demand for SQL has raised the demand for skilled database developers too. There is a need for individuals who can control database systems effectively. For this purpose, you should be prepared well before you go for an SQL interview. We have compiled a list of top 100 SQL interview questions with researched answers that are frequently asked by developers. The discussion will start from the basics then you can see some advanced level questions too that are suitable for intermediates having 2-5 years of experience or even more. To go through the complete list of “Top 100 SQL interview questions”,  Click Here. Happy Reading!

Conclusion

This SQL tutorial guide for beginners is suitable for students who want to learn SQL online. Here, we have discussed the top concepts that are frequently used by expert database developers. The discussion doesn’t end here; you can expand your knowledge base further by joining the SQL certification program at JanBask Training.

You will also get familiar with using SQL at the workplace. We wish you a successful career in the database domain with an attractive salary package. To know more about our SQL course, contact our experts now!