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Hope this post finds you in good health and spirit.

Structured Query Language, abbreviated as SQL, is a domain-specific language used in programming and designed for managing data held in a relational database management system, or for stream processing in a relational data stream management system.

An good developer must be familiar with a few commands in SQL because it is such a strong development tool. The SQL queries listed below are important for coding and optimization. Almost every system that interacts with a SQL database will be affected by each query in the SQL tutorial.

SQL ALTER TABLE Statement

The ALTER TABLE statement is used to add, delete, or modify columns in an existing table.

The ALTER TABLE statement is also used to add and drop various constraints on an existing table.

ALTER TABLE – ADD Column
To add a column in a table, use the following syntax:

ALTER TABLE table_name
ADD column_name datatype;

The following SQL adds an “Email” column to the “Customers” table:

ALTER TABLE Customers
ADD Email varchar(255);
ALTER TABLE - DROP COLUMN

To delete a column in a table, use the following syntax (notice that some database systems don’t allow deleting a column):

ALTER TABLE table_name
DROP COLUMN column_name;

The following SQL deletes the “Email” column from the “Customers” table:

ALTER TABLE Customers
DROP COLUMN Email;
ALTER TABLE - RENAME COLUMN

To rename a column in a table, use the following syntax:

ALTER TABLE table_name
RENAME COLUMN old_name to new_name;
ALTER TABLE - ALTER/MODIFY DATATYPE

To change the data type of a column in a table, use the following syntax:

SQL Server / MS Access:

ALTER TABLE table_name
ALTER COLUMN column_name datatype;
My SQL / Oracle (prior version 10G):

ALTER TABLE table_name
MODIFY COLUMN column_name datatype;
Oracle 10G and later:

ALTER TABLE table_name
MODIFY column_name datatype;

You must have a thorough comprehension of all SQL concepts if you want to work as a data analyst, data scientist, data engineer, data administrator, or web developer. If you want to ace a SQL job interview, you should familiarize yourself with the SQL questions that are frequently used to assess your technical abilities. 

So, that’s all in this blog. I will meet you soon with next stuff. Have a nice day!!!

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