SQL, or Structured Query Language, is a standardized language for defining, accessing, and managing relational databases, widely recognized as an American and international standard. It offers flexibility with free-form syntax and enables users to perform various database operations using Data Definition Language (DDL), Data Manipulation Language (DML), and Data Control Language (DCL). SQL's advantages include high-level abstraction, portability across systems, and the ability to process multiple records efficiently.

1. SQL OVERVIEW

2. SQL
The name SQL pronounced as “ess-cue-ell” or ‘sequel’ is the abbreviation for structured
query language. The SQL consists of a set of facilities for defining, accessing and managing
relational databases. All tasks related to relational data management-creating tables,
querying the database, deleting, granting access to users etc., can be done using SQL. It has
been accepted as an American standard by American National Standards Institute (ANSI)
and
is a Federal Information Processing Standard (FIPS). It is also an international standard
recognized by the ISO. The first commercial DBMS that supported SQL was Oracle in 1979.
SQL statements can be invoked either interactively in a terminal session or by embedding
them in application programs.

3. CHARACTERISTICS OF SQL
The following are the important characteristics of SQL.
1. SQL is extremely flexible.
2. SQL uses a free form syntax that gives the user the ability to structure SQL
statements in a way best suited.
3. It is a free formatted language, i.e., there is no need to start SQL statements in a
particular column or to be finished in a single line.
4. It has relatively few commands.
5. It is a non-procedural language.

4. ADVANTAGES OF SQL
The advantages of SQL are as follows:
1. SQL is a high level language that provides a greater degree of abstraction than
procedural languages. The programmer has to specify what data is needed but need not to
specify, how to retrieve it.
2. SQL is a unified language. The same language can be used to define data structures,
querying data, control access to the data, insert, delete and modify occurrences of the data
and so on.
3. All the programs written in SQL are portable, thus they can be moved from one database
to another with very little modification. Such porting could be required when DBMS needs to
be upgraded or changed.
4. The language is simple and easy to learn. It can handle complex situations very efficiently.

5. ADVANTAGES OF SQL
4. The language is simple and easy to learn. It can handle complex situations very
efficiently.
5. The language has sound theoretical base and there is no ambiguity about the way a
query will interpret the data and produce the results. Thus the results to be expected are
well defined.
6. SQL processes sets-of-records rather than just one record-at-a time. This set-at-a time
feature of the SQL makes it more powerful.
7. SQL as a language is independent of the way it is implemented internally. This is
because SQL specifies what is required and not how it should be done.
8. SQL enables its users to deal with a number of database management systems where
it is available.

6. SQL ENVIRONMENT

7. SQL LANGUAGE TYPES
Data definition language (DDL)
Commands used to define a database, including those for creating, altering, and
dropping tables and establishing constraints.
Data manipulation language (DML)
Commands used to maintain and query a database, including those for updating,
inserting, modifying, and querying data.
Data control language (DCL)
Commands used to control a database, including those for administering privileges
and committing (saving) data.

8. LANGUAGE TYPES

9. PARTS (COMPONENTS) OF SQL LANGUAGE
Query Dispatcher
Optimization Engines
Classic Query Engine
SQL Query Engine,

10. SQL DATA TYPES
Data types are used to represent the nature of the data that can be stored in the
database table. For example, in a particular column of a table, if we want to store a
string type of data then we will have to declare a string data type of this column.
Data types mainly classified into three categories for every database.
String Data types
Numeric Data types
Date and time Data types
research on specific examples on each category.

11. SQL OPERATORS
The SQL reserved words and characters are called operators, which are used with a
WHERE clause in a SQL query.
In SQL, an operator can either be a unary or binary operator.
The unary operator uses only one operand for performing the unary operation,
whereas the binary operator uses two operands for performing the binary operation.
Syntax
Operator SQL_Operand (Unary operator)
Operand1 SQL_Operator Operand2 (Binary Operator)

12. OPERATORS

13. TYPES OF OPERATOR
SQL Arithmetic Operators
SQL Comparison Operators
SQL Logical Operators
SQL Set Operators
SQL Bit-wise Operators
SQL Unary Operators

14. SQL SYNTAX
Syntax Guidelines
You can write the keywords of SQL in both uppercase and lowercase, but writing the
SQL keywords in uppercase improves the readability of the SQL query.
SQL statements or syntax are dependent on text lines. We can place a single SQL
statement on one or multiple text lines.
You can perform most of the action in a database with SQL statements.
SQL syntax depends on relational algebra and tuple relational calculus.

15. SQL STATEMENTS
SQL statements tell the database what operation you want to perform on the
structured data and what information you would like to access from the database.
Each SQL statement begins with any of the SQL keywords and ends with the
semicolon (;).
The semicolon is used in the SQL for separating the multiple Sql statements which are
going to execute in the same call.
Example:
SELECT "column_name" FROM "table_name";

16. DDL STATEMENTS
Create: ( Database, table)
Drop: ( Database, table)
Alter: ( Database, table)

17. CREATE: ( DATABASE)
In SQL, the 'Create Database' statement is a first step for storing the structured data
in the database.
Sytanx
CREATE DATABASE Database_Name;
In this syntax, Database_Name specifies the name of the database which we want to
create in the system. We have to type the database name in query just after the
'Create Database' keyword.
CREATE DATABASE Student ;
This example creates the Student database. To create the Student database, you
have to type the following command in Structured Query Language:

18. SQL DROP DATABASE
In this SQL syntax, we have to specify the name of that database which we want to
delete permanently from the database system. We have to write the name of the
database after the DROP DATABASE keyword in every example.
DROP DATABASE Database_Name1, [ Database_Name2, ......., Database_NameN ] ;
DROP DATABASE Student;

19. SQL RENAME TABLE
In some situations, database administrators and users want to change the name of the
table in the SQL database because they want to give a more relevant name to the
table.
RENAME old_table _name To new_table_name ;
RENAME Cars To Car_2021_Details ;

20. DML: SELECT STATEMENT
The SELECT statement is the most commonly used command in Structured Query
Language. It is used to access the records from one or more database tables and
views.
It also retrieves the selected data that follow the conditions we want.
Syntax of SELECT Statement in SQL
SELECT Column_Name_1, Column_Name_2, ....., Column_Name_N FROM Table_Name;
In this SELECT syntax, Column_Name_1, Column_Name_2, ….., Column_Name_N are the
name of those columns in the table whose data we want to read.
If you want to access all rows from all fields of the table, use the following SQL SELECT syntax
with * asterisk sign

21. SELECT STATEMENT
Examples of SELECT Statement in SQL
Here, we took the following two different SQL examples which will help you to execute the SELECT statement for
retrieving the records:
CREATE TABLE Student_Records
(
Student_Id Int PRIMARY KEY,
First_Name VARCHAR (20),
Address VARCHAR (20),
Age Int NOT NULL,
Percentage Int NOT NULL,
Grade VARCHAR (10)
) ;

22. The following query inserts the record of intelligent students into
the Student_Records table:
INSERT INTO Student VALUES (201, Jina, lilongwe, 18, 89, A),
(202, Bado, Karonga, 19, 93, A),
(203, Yash, Mzuzu, 20, 89, A),
(204, Bhima, Blantyre, 19, 78, B),
(05, Yasini, Mangich, 20, 75, B),
(206, Letina, Bale, 19, 51, C),
(207, Vivian, Neno, 20, 62, B);

23. The following SQL query displays all the values of each column from the above
Student_records table:
SELECT * FROM Student_Records;
The following query displays the values of particular column from the
above Student_Record table:
SELECT Student_Id, Age, Percentage, Grade FROM Student_Records;

24. SQL CLAUSE
Clauses are in-built functions available to us in SQL. With the help of clauses, we
can deal with data easily stored in the table.
Clauses help us filter and analyze data quickly.
When we have large amounts of data stored in the database, we use Clauses to
query and get data required by the user

25. SQL WHERE
A WHERE clause in SQL is a data manipulation language statement.
WHERE clauses are not mandatory clauses of SQL DML statements. But it can be used
to limit the number of rows affected by a SQL DML statement or returned by a query.
Actually. it filters the records. It returns only those queries which fulfill the specific
conditions.
WHERE clause is used in SELECT, UPDATE, DELETE statement etc.

26. SYNTAX
SELECT column1, column 2, ... column n
FROM table_name
WHERE [conditions]
Column Operators : < , >, >=, <=, !=, <>,
BETWEEN, IN, LIKE
Example
SELECT First_Name, age FROM Student_Records
WHERE grade >= 60;
SELECT * FROM Employee_Details WHERE Emp_Panelty = 500;

27. HAVING CLAUSE
The HAVING clause places the condition in the groups defined by the GROUP BY
clause in the SELECT statement.
This SQL clause is implemented after the 'GROUP BY' clause in the 'SELECT' statement.
This clause is used in SQL because we cannot use the WHERE clause with the SQL
aggregate functions. Both WHERE and HAVING clauses are used for filtering the
records in SQL queries.

28. SYNTAX
SELECT column_Name1, column_Name2, ....., column_NameN aggregate_function_na
me(column_Name) FROM table_name GROUP BY column_Name1 HAVING condition;
Examples
Example 1: Let's take the following Employee table, which helps you to analyze the
HAVING clause with SUM aggregate function:

29. EMPLOYEE TABLE
Emp_Id Emp_Name Emp_Salary Emp_City
201 Bhahat 2000 Mzuzu
202 Nikita 4000 Lilongwe
203 Thom 8000 Blantyre
204 Banda 2000 Mzuzu
205 Phiri 5000 Lilongwe

30. EXAMPLE
SELECT SUM(Emp_Salary), Emp_City FROM Employee GROUP BY Emp_City;
SUM(Emp_Salary) Emp_City
4000 Mzuzu
9000 Lilongwe
8000 Blantyre

31. EXAMPLE
Now, suppose that you want to show those cities whose total salary of employees is
more than 5000. For this case, you have to type the following query with the HAVING
clause in SQL:
SELECT SUM(Emp_Salary), Emp_City FROM Employee GROUP BY Emp_City HAVIN
G SUM(Emp_Salary)>5000;
Output?

32. ORDER BY CLAUSE
Whenever we want to sort the records based on the columns stored in the tables of
the SQL database, then we consider using the ORDER BY clause in SQL.
The ORDER BY clause in SQL will help us to sort the records based on the specific
column of a table.
This means that all the values stored in the column on which we are applying ORDER
BY clause will be sorted, and the corresponding column values will be displayed in the
sequence in which we have obtained the values in the earlier step.
Using the ORDER BY clause, we can sort the records in ascending or descending order
as per our requirement. The records will be sorted in ascending order whenever
the ASC keyword is used with ORDER by clause. DESC keyword will sort the records
in descending order.

33. SYNTAX
Syntax to sort the records in ascending order:
SELECT ColumnName1,...,ColumnNameN FROM TableName ORDER BY ColumnName
ASC;
Syntax to sort the records in descending order:
SELECT ColumnName1,...,ColumnNameN FROM TableName ORDER BY ColumnName
DESC;
Syntax to sort the records in ascending order without using ASC keyword:
SELECT ColumnName1,...,ColumnNameN FROM TableName ORDER BY ColumnName
;

34. SQL JOIN
As the name shows, JOIN means to combine something. In case of SQL, JOIN
means "to combine two or more tables".
The SQL JOIN clause takes records from two or more tables in a database and
combines it together.
1. inner join,
2. left outer join,
3. right outer join,
4. full outer join,
5. cross join.

35. JOIN USE
If you want to access more than one table through a select statement.
If you want to combine two or more table then SQL JOIN statement is used .
It combines rows of that tables in one table and one can retrieve the information by a
SELECT statement.
The joining of two or more tables is based on common field between them.
SQL INNER JOIN also known as simple join is the most common type of join.

36. INNER JOIN
SELECT table1.column1,table1.column2,table2.column1,....
FROM table1
INNER JOIN table2
ON table1.matching_column = table2.matching_column;
table1: First table.
table2: Second table
matching_column: Column common to both the tables.