SQL stands for Structured Query Language , and it is used to communicate with the Database. This is a standard language used to perform tasks such as retrieval, updation, insertion and deletion of data from a database.
Standard SQL Commands are Select.

Database is nothing but an organized form of data for easy access, storing, retrieval and managing of data. This is also known as structured form of data which can be accessed in many ways.
Example: School Management Database, Bank Management Database.

A table is a set of data that are organized in a model with Columns and Rows. Columns can be categorized as vertical, and Rows are horizontal. A table has specified number of column called fields but can have any number of rows which is called record.

This is a keyword used to query data from more tables based on the relationship between the fields of the tables. Keys play a major role when JOINs are used.

The following are the table types used in SQL

•  Partitioned tables
•  Temporary tables
•  System tables
• Wide tables

A composite key is the combination of two or more columns in a table used to identify a row in a table. Know that a combination of columns is essential in creating composite keys because a single column in a composite key cannot identify a row in a table. We can say that the composite key is the primary key with a few more attributes or columns. Also, a composite key can be a combination of candidate keys.

SQL constraints specify conditions for a column or table to manage the data stored in tables effectively.
The following are the commonly used SQL constraints.

•  NOT NULL – This condition ensures columns won’t accept a NULL value.
• UNIQUE – It ensures that all the values in a column must be unique.
• CHECK – It ensures that all the column fields obey a specific condition.
• DEFAULT – It provides a default value for the fields of a column unless no value is specified for the fields
• CREATE INDEX – It ensures creating an index for tables so that retrieving data from the tables becomes easier
• PRIMARY KEY – It must identify every row of a table
• FOREIGN KEY – It must link tables based on common attributes

The following aggregate functions are used in SQL

• COUNT
•  SUM
• AVG
• MAX
•  MIN

DBMS (Database Management System) can be defined as software designed for storing and accessing user’s data while taking the necessary security measures.

A foreign key is used to link two database tables. A foreign key can also be defined as a column or combination of columns whose value matches with the primary key in a different table.

 Database normalization can be defined as a process that needs to be carried out for each and every database you design. The mechanism of applying a set of formal criteria and rules is called Normal Forms.

The following are the types of Normalizations in SQL:

• First Normal Form (1 NF)
• Second Normal Form (2 NF)
• Third Normal Form (3 NF)
• Boyce Codd Normal Form or Fourth Normal Form ( BCNF or 4 NF)
• Fifth Normal Form (5 NF)
• Sixth Normal Form (6 NF)

• The syntax for COALESCE function is mentioned below:  COALESCE(exp1, exp2, …. expn)
• The function returns the first non-null expressions that are given in the parameter list.