Structured Query Language(SQL -Basics)

 What is SQL?

SQL (Structured Query Language) is a standard programming language used to manage and manipulate relational databases. Here are some basic concepts and commands of SQL:

• Databases and Tables: A database is a collection of tables, and each table consists of columns and rows.
• Data Types: Each column in a table has a data type, which defines the type of data that can be stored in that column. Common data types include integers, strings, dates, and booleans.
• SELECT statement: The SELECT statement is used to query data from a database. It allows you to specify which columns you want to retrieve from a table and can be combined with other statements like WHERE, GROUP BY, and ORDER BY to filter, aggregate, and sort the data.
• INSERT statement: The INSERT statement is used to add new data to a table. It specifies which columns you want to add data to and the values to be inserted.
• UPDATE statement: The UPDATE statement is used to modify existing data in a table. It specifies which columns you want to update and the new values to be set.
• DELETE statement: The DELETE statement is used to remove data from a table. It specifies which rows you want to delete.
• JOINs: JOINs are used to combine data from multiple tables into a single result set based on a common column. There are several types of JOINs, including INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN.
• GROUP BY statement: The GROUP BY statement is used to group data in a table based on one or more columns. It is often used with aggregate functions like SUM, COUNT, AVG, and MAX to calculate summary statistics for each group.
• ORDER BY statement: The ORDER BY statement is used to sort the result set based on one or more columns. It can sort the data in ascending or descending order.

These are some of the basic concepts and commands of SQL. With these commands, you can retrieve, insert, update, and delete data from a database, as well as join tables and calculate summary statistics.

SQL Basic Syntax:

SQL commands are written as statements that start with a keyword like SELECT, INSERT, UPDATE, or DELETE, followed by one or more clauses that define the action to be taken. For example:

sql:

SELECT column_name1, column_name2

FROM table_name

WHERE condition;

This statement selects specific columns from a table based on a given condition.

Creating and modifying tables:

To create a table, use the CREATE TABLE statement followed by the table name and column definitions, like so:

sql:

CREATE TABLE table_name (

    column1 datatype,

    column2 datatype,

    ...

);

To add/remove a column to/from an existing table, use the ALTER TABLE statement:

sql:

ALTER TABLE table_name

ADD/DROP column_name datatype;

Retrieving data:

The SELECT statement is used to retrieve data from a database. It can be used with various clauses, including WHERE, ORDER BY, GROUP BY, and JOIN. For example:

sql:

SELECT column_name1, column_name2

FROM table_name

WHERE condition

ORDER BY column_name ASC/DESC;

This statement selects specific columns from a table based on a given condition and orders them by a specified column in ascending or descending order.

Updating data:

The UPDATE statement is used to modify data in a table. For example:

sql:

UPDATE table_name

SET column_name = value

WHERE condition;

This statement updates the value of a specified column in a table based on a given condition.

Deleting data:

The DELETE statement is used to remove data from a table. For example:

sql:

DELETE FROM table_name

WHERE condition;

This statement removes rows from a table based on a given condition.

These are just the basics of SQL, but it should give you a good foundation to start exploring the language and building your own queries.