Added SQL under DBMS under Docs

docs/DBMS/Structured Query Language/_category.json

@@ -0,0 +1,8 @@
+{
+    "label": "SQL",
+    "position": 8,
+    "link": {
+        "type": "generated-index",
+        "description": "Explore SQL in DBMS."
+    }
+}

docs/DBMS/Structured Query Language/sql-aggregate-functions.md

@@ -0,0 +1,84 @@
+---
+id: sql-aggregate-function
+title: DBMS - SQL Aggregate Functions
+sidebar_label: Aggregate Functions
+sidebar_position: 3
+description: Learn about the SQL Aggregate Functions.
+tags:
+  - DBMS
+  - SQL
+  - SQL-Functions
+  - Database Design
+---
+
+# DBMS - SQL Aggregate Functions
+
+Aggregate functions in SQL are used to perform calculations on multiple rows of a table's column and return a single value. These functions are essential for data analysis and reporting as they help in summarizing large datasets.
+
+## COMMON AGGREGATE FUNCTIONS
+
+1. **COUNT():** The COUNT() function returns the number of rows that match a specified condition. This query returns the total number of rows in the table.
+    ```sql
+    SELECT COUNT(*) AS total_rows
+    FROM table_name;
+    ```
+
+2. **SUM():** The SUM() function returns the total sum of a numeric column. This query calculates the sum of all values in column_name.
+    ```sql
+    SELECT SUM(column_name) AS total_sum
+    FROM table_name;
+    ```
+
+3. **AVG():** The AVG() function returns the average value of a numeric column. This query calculates the average value of column_name.
+    ```sql
+    SELECT AVG(column_name) AS average_value
+    FROM table_name;
+    ```
+
+4. **MIN():** The MIN() function returns the smallest value in a specified column. This query finds the smallest value in column_name.
+    ```sql
+    SELECT MIN(column_name) AS minimum_value
+    FROM table_name;
+    ```
+
+5. **MAX():** The MAX() function returns the largest value in a specified column. This query finds the largest value in column_name.
+    ```sql
+    SELECT MAX(column_name) AS maximum_value
+    FROM table_name;
+    ```
+
+## AGGREGATE FUNCTIONS WITH GROUP BY
+
+Aggregate functions are often used in conjunction with the GROUP BY clause to group the result set by one or more columns and perform the calculation on each group.
+    ```sql
+     SELECT department, COUNT(*) AS total_employees
+     FROM employees
+     GROUP BY department; 
+    ```
+    This query groups the employees by their department and returns the number of employees in each department.
+
+    ```sql
+    SELECT department, COUNT(*) AS total_employees, AVG(salary) AS average_salary, MAX(salary) AS highest_salary
+    FROM employees
+    GROUP BY department;
+    ```
+    This query groups the employees by their department and returns the total number of employees, average salary, and highest salary in each department.
+
+## AGGREGATE FUNCTIONS USING HAVING
+
+The HAVING clause is used to filter groups based on the result of aggregate functions. It is similar to the WHERE clause, but WHERE cannot be used with aggregate functions.
+    ```sql
+    SELECT department, COUNT(*) AS total_employees
+    GROUP BY department
+    HAVING COUNT(*) > 10;
+    ```
+    This query groups the employees by their department and returns the departments that have more than 10 employees.
+
+You can combine multiple aggregate functions in a single query to perform various calculations. 
+    ```sql
+    SELECT COUNT(*) AS total_rows, SUM(column_name) AS total_sum, AVG(column_name) AS average_value
+    FROM table_name;
+    ```
+    This query returns the total number of rows, the sum of column_name, and the average value of column_name.
+
+Aggregate functions are powerful tools in SQL for summarizing and analyzing data. By mastering these functions, you can perform complex data analysis and gain valuable insights from your database.

docs/DBMS/Structured Query Language/sql-basic-concepts.md

@@ -0,0 +1,71 @@
+---
+id: sql-basic-concepts
+title: DBMS - SQL Basic Concepts
+sidebar_label: Basic Concepts
+sidebar_position: 1
+description: Learn about the Structured Query language (SQL), its basic concepts, data types, operators, and commands that form the foundation of database manipulation.
+tags:
+  - DBMS
+  - SQL
+  - Database Design
+---
+
+# DBMS - SQL Basic Concepts
+
+SQL stands for Structured Query Language. It is used to access and manipulate data in databases. By executing queries SQL can *create*, *update*, *delete*, and *retrieve* data in databases like MySQL, Oracle, PostgreSQL, etc. Overall, SQL is a query language that communicates with databases.
+
+## Why SQL?
+SQL helps to easily get information from data with high efficiency. Best Part? Without a lot of coding knowledge, we can manage a database with SQL. Anyone who knows English can master SQL queries in no time.
+When we are executing the command of SQL on any Relational database managemnet system, then the system automatically finds the best routine to carry out our requests, and the SQL engine determines how to interpret the particular command.
+
+
+## SQL DATABASE
+The very first step is to store the information in database, hence, we will first create a database.
+
+1. **CREATE:**
+   To create a new database in SQL we use this command. Note that blank spaces are not allowed in the name and is case-insenitive.
+   ```sql
+   CREATE DATABASE database_name;
+2. **SHOW:**
+   To view all the databases, we can use the keyword show. It returns a list of all the databases that exist in our system.
+   ```sql
+   SHOW DATABASE;
+3. **USE:**
+   To change the database or select another database, we use the command:
+   ```sql
+   USE database_name;
+4. **DROP:**
+    It is used to remove the entire database from the system. Once deleted, it can not be retrieved.
+    We can use the if exists clause to avoid any errors.
+    ```sql
+    DROP DATABASE database_name;
+    DROP DATABASE IF EXISTS database_name; 
+5. **RENAME:**
+    It is used to rename the database.
+    ```sql
+    RENAME DATABASE former_database_name TO new_database_name;
+
+## SQL TABLES
+Now we have created the database. We will create tables inside our database. They are very similar to spreadsheets, which store data in very organized grid format. We can create as many tables as we require.
+1. **CREATE:**
+   To create a new table in database we use this command. We define the structure of table and the datatypes of columns.
+   ```sql
+   CREATE table Employee(
+    EmployeeID INT PRIMARY KEY,
+    FirstName VARCHAR(50),
+    LastName VARCHAR(50),
+    Department VARCHAR(50),
+    Salary DECIMAL(10, 2)
+   );
+2. **DELETE:**
+   It is used to delete data in a database. We selectively remove records from a database table based on certain conditions.
+   ```sql
+   DELETE FROM table_name WHERE some_condition;
+3. **DROP:**
+    It is used to delete data and structure of the table from the database permanently.
+    ```sql
+    DROP TABLE table_name;
+4. **ALTER:**
+    It is used to rename the table.
+    ```sql
+    ALTER TABLE former_table_name RENAME TO new_table_name;

docs/DBMS/Structured Query Language/sql-clauses-operators.md

@@ -0,0 +1,203 @@
+---
+id: sql-clauses-operators
+title: DBMS - SQL Clauses & Operators
+sidebar_label: Clauses & Operators
+sidebar_position: 2
+description: Learn about the SQL clauses and operators.
+tags:
+  - DBMS
+  - SQL-Operators
+  - SQL
+  - Database Design
+---
+
+# DBMS - SQL Clauses & Operators
+
+In SQL, clauses and operators play a crucial role in forming queries that manipulate and retrieve data from databases. Understanding these elements is essential for effective database management and query execution.
+
+## SQL Clauses
+
+SQL clauses are used to specify various conditions and constraints in SQL statements. Here are some of the most commonly used clauses:
+
+1. **SELECT:**
+   The SELECT clause is used to retrieve data from a database.
+   ```sql
+   SELECT column1, column2, ...
+   FROM table_name;
+2. **WHERE:**
+   The WHERE clause is used to filter records based on a specified condition.
+   ```sql
+   SELECT column1, column2, ...
+   FROM table_name
+   WHERE condition;
+3. **ORDER BY:**
+   The ORDER BY clause is used to sort the result set in ascending or descending order.
+   ```sql
+   SELECT column1, column2, ...
+   FROM table_name
+   ORDER BY column1 ASC | DESC;
+4. **GROUP BY:**
+   The GROUP BY clause is used to group rows that have the same values into summary rows.
+   ```sql
+   SELECT column1, COUNT(*)
+   FROM table_name
+   GROUP BY column1;
+5. **HAVING:**
+   The HAVING clause is used to filter groups based on a specified condition, often used with GROUP BY.
+   ```sql
+   SELECT column1, COUNT(*)
+   FROM table_name
+   GROUP BY column1
+   HAVING condition;
+6. **JOIN:**
+   The JOIN clause is used to combine rows from two or more tables based on a related column.
+  - **INNER JOIN:**
+      ```sql
+      SELECT columns
+      FROM table1
+      INNER JOIN table2
+      ON table1.column = table2.column;
+  - **LEFT JOIN (or LEFT OUTER JOIN):**
+      ```sql
+      SELECT columns
+      FROM table1
+      LEFT JOIN table2
+      ON table1.column = table2.column;
+  - **RIGHT JOIN (or RIGHT OUTER JOIN):**
+      ```sql
+      SELECT columns
+      FROM table1
+      RIGHT JOIN table2
+      ON table1.column = table2.column;
+  - **FULL JOIN (or FULL OUTER JOIN):**
+      ```sql
+      SELECT columns
+      FROM table1
+      FULL JOIN table2
+      ON table1.column = table2.column;
+      ```
+
+## SQL Operators
+
+SQL operators are used to perform operations on data. Here are some of the most commonly used operators:
+
+1. **ARITHMETIC OPERATORS:**
+    Arithmetic operators are used to perform arithmetic operations on numeric data.
+
+  - **ADDITION:**
+    ```sql
+    SELECT column1 + column2 AS result
+    FROM table_name;
+    ```
+  - **SUBTRACTION:**
+    ```sql
+    SELECT column1 - column2 AS result
+    FROM table_name;
+    ```
+  - **MULTIPLICATION:**
+    ```sql
+    SELECT column1 * column2 AS result
+    FROM table_name;
+    ```  
+  - **DIVISION:**
+    ```sql
+    SELECT column1 / column2 AS result
+    FROM table_name;
+    ```
+
+2. **COMPARISON OPERATORS:**
+    Comparison operators are used to compare two values. 
+
+  - **EQUAL TO:**
+    ```sql
+    SELECT columns
+    FROM table_name
+    WHERE column = value;
+    ```  
+  - **NOT EQUAL TO:**
+    ```sql
+    SELECT columns
+    FROM table_name
+    WHERE column <> value;
+    ```    
+  - **GREATER THAN:**
+    ```sql
+    SELECT columns
+    FROM table_name
+    WHERE column > value;
+    ```    
+  - **LESS THAN:**
+    ```sql
+    SELECT columns
+    FROM table_name
+    WHERE column < value;
+    ```    
+  - **GREATER THAN OR EQUAL TO:**
+    ```sql
+    SELECT columns
+    FROM table_name
+    WHERE column >= value;
+    ```    
+  - **LESS THAN OR EQUAL TO:**
+    ```sql
+    SELECT columns
+    FROM table_name
+    WHERE column <= value;
+    ```
+
+3. **LOGICAL OPERATORS:**
+    Logical operators are used to combine two or more conditions.
+
+  - **AND:**
+    ```sql
+    SELECT columns
+    FROM table_name
+    WHERE condition1 AND condition2;  
+    ```    
+  - **OR:**
+    ```sql
+    SELECT columns
+    FROM table_name
+    WHERE condition1 OR condition2;
+    ```    
+  - **NOT:**
+    ```sql
+    SELECT columns
+    FROM table_name
+    WHERE NOT condition;
+    ```
+
+4. **OTHER USEFUL OPERATORS:**
+
+  - **BETWEEN:** The BETWEEN operator selects values within a given range.
+    ```sql
+    SELECT columns
+    FROM table_name
+    WHERE column BETWEEN value1 AND value2;
+    ```  
+  - **IN:** The IN operator allows you to specify multiple values in a WHERE clause.
+    ```sql
+    SELECT columns
+    FROM table_name
+    WHERE column IN (value1, value2, ...);
+    ```  
+  - **LIKE:** The LIKE operator is used to search for a specified pattern in a column.
+    ```sql
+    SELECT columns
+    FROM table_name
+    WHERE column LIKE pattern;
+    ```  
+  - **IS NULL:** The IS NULL operator is used to test for empty values (NULL).
+    ```sql
+    SELECT columns
+    FROM table_name
+    WHERE column IS NULL;
+    ```
+  - **IS NOT NULL:** The IS NOT NULL operator is used to test for non-empty values.
+    ```sql
+    SELECT columns
+    FROM table_name
+    WHERE column IS NOT NULL;
+    ```
+
+This covers the basic SQL clauses and operators, which are essential for writing effective SQL queries. By mastering these elements, you can perform complex data manipulations and retrieve valuable insights from your database.