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Aggregate Functions are all about

Performing  calculations on multiple rows

Of a single column of a table

And returning a single value.

The ISO standard defines five (5) aggregate functions namely;

1) COUNT 2) SUM 3) AVG 4) MIN 5) MAX 

Why use aggregate functions.

From a business perspective, different organization levels have different information requirements. Top levels managers are…

The WHERE clause is used to filter records. The WHERE clause is used to extract only those records that fulfill a specified condition.

Syntax:-

SELECT column1, column2, … FROM table_name WHERE condition;

Example:-

SELECT * FROM Customers WHERE Country=’Mexico’;

Operators in The WHERE Clause a)   SQL Arithmetic Operators:-

Assume ‘variable a’ holds 10 and ‘variable b’ holds 20,…

The PRIMARY KEY constraint uniquely identifies each record in a table. Primary keys must contain UNIQUE values, and cannot contain NULL values. A table can have only ONE primary key; and in the table, this primary key can consist of single or multiple columns (fields).

SQL PRIMARY KEY ON CREATE TABLE:-

The SQL creates a PRIMARY KEY on the “ID” column when the “Persons” table is created.

DQL is used to fetch the data from the database.

It uses only one command:

SELECT: The SELECT statement is used to select data from a database. The data returned is stored in a result table, called the result-set.

Syntax:

SELECT column1, column2, … FROM table_name;

Here, column1, column2, … are the field names of the table you want to select data from. If you want to select all the…

TCL commands can only use with DML commands like INSERT, DELETE and UPDATE only.

These operations are automatically committed in the database that’s why they cannot be used while creating tables or dropping them.

Here are some commands that come under TCL:

COMMIT:- If everything is in order with all statements within a single transaction, all changes are recorded together in the database…

DCL commands are used to grant and take back authority from any database user.

Here are some commands that come under DCL:

Grant:- SQL Grant command is used to provide access or privileges on the database objects to the users.

Syntax:-

“GRANT privilege_name ON object_name “””TO {user_name | PUBLIC | role_name} [with GRANT option];  

Example:

GRANT SELECT ON employee TO user1

Revo…

DML commands are used to modify the database. It is responsible for all form of changes in the database.

The command of DML is not auto-committed that means it can’t permanently save all the changes in the database. They can be rollback.

Here are some commands that come under DML:

INSERT:- The INSERT INTO statement is used to insert new records in a table.

Syntax:

It is possible to…

DDL changes the structure of the table like creating a table, deleting a table, altering a table, etc.

All the command of DDL are auto-committed that means it permanently save all the changes in the database.

Here are some commands that come under DDL:

CREATE:-  The CREATE TABLE statement is used to create a new table in a database.

Syntax:

CREATE TABLE table_name (     column1 datatype,