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SQL

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SQL is a domain-specific language used for managing and manipulating relational databases. It provides a standardized way to interact with databases, enabling users to perform tasks such as querying data, updating records, and defining the structure of a database.

**Key Concepts in SQL:**

1. **Database:**
– A collection of related tables that store data in a structured format.

2. **Table:**
– A fundamental component of a database that organizes data into rows and columns.

3. **Schema:**
– A logical grouping of database objects, such as tables, views, and procedures.

4. **Queries:**
– SQL allows you to retrieve specific data from a database using SELECT statements. For example:
“`sql
SELECT column1, column2 FROM table WHERE condition;
“`

5. **Data Manipulation Language (DML):**
– SQL includes statements like INSERT, UPDATE, and DELETE to modify data in the database.

6. **Data Definition Language (DDL):**
– SQL includes statements like CREATE, ALTER, and DROP to define and manage the structure of the database.

7. **Normalization:**
– The process of organizing data in a database to reduce redundancy and dependency.

8. **Indexes:**
– Database indexes enhance the speed of data retrieval operations on a table.

**Basic SQL Commands:**

1. **SELECT:**
– Used to retrieve data from one or more tables.

2. **INSERT:**
– Adds new rows of data to a table.

3. **UPDATE:**
– Modifies existing data in a table.

4. **DELETE:**
– Removes rows from a table.

5. **CREATE:**
– Creates a new database, table, or other database objects.

6. **ALTER:**
– Modifies the structure of a database object.

7. **DROP:**
– Deletes a database object.