https://github.com/chaseofthejungle/intro-to-sql
An overview guide of essential SQL databasing and querying concepts.
https://github.com/chaseofthejungle/intro-to-sql
databases rdbms sql
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An overview guide of essential SQL databasing and querying concepts.
- Host: GitHub
- URL: https://github.com/chaseofthejungle/intro-to-sql
- Owner: chaseofthejungle
- Created: 2025-01-20T19:06:59.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2025-03-19T20:52:51.000Z (over 1 year ago)
- Last Synced: 2025-03-19T21:40:22.393Z (over 1 year ago)
- Topics: databases, rdbms, sql
- Homepage:
- Size: 2.93 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
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Metadata Files:
- Readme: README.md
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README
# Intro to Structured Query Language (SQL)
**Overview:** A *database* is an organized data source/structure that should be easily accessible (by appropriately authenticated and authorized users, when relevant) for data management, retrieval, and long-term storage. *Relational Database Management Systems (RDBMSes)* are specialized databases that store data in tables (and sometimes other structures, such as forms and queries in Microsoft Access software) and share data between tables using common columns. *Structured Query Language (SQL)* is a standardized language that performs RDBMS tasks such as creating, reading, updating, and deleting data (also known as 'CRUD' operations).
#### Table of Contents
1. [NoSQL vs. SQL](#no-sql)
2. [CRUD Operations](#crud)
3. [Database Terms](#key-terms)
4. [SQL Clauses](#sql-clauses)
5. [SQL Constraints](#sql-constraints)
6. [SQL Filtering and Sorting](#sql-filtering-sorting)
7. [SQL Joins](#sql-joins)
8. [Supplemental Resources](#supplemental)
## 1. NoSQL vs. SQL
Several key differences between SQL and Not Only SQL (NoSQL) databases include:
| Feature | SQL | NoSQL |
| :---: | :---: | :---: |
| Direction of Scalability | Vertical | Horizontal |
| Popular Objects | Tables | Column Stores, Documents, Graphs, Key-Value Pairs |
| Schemas | Predefined | Dynamic |
| Transaction Handling | Rows (Single or Multiple) | Unstructured Data (e.g., JSON) |
Some common reasons for choosing a NoSQL database include: quick response times/low latency, instant/real-time analytics, constantly-evolving data, and server scalability needs.
* **Examples of NoSQL Databases include:**
- [Actian NoSQL Object Database](https://www.actian.com/databases/nosql/): Supports transactional storage of data using object-oriented programming (OOP) languages.
- [Apache Cassandra](https://cassandra.apache.org/_/index.html): Optimizes parallel/commodity computing to handle and serve massive data volumes.
- [Apache HBase](https://hbase.apache.org/): Enables fault-tolerant storage of sparse data.
- [Couchbase](https://www.couchbase.com/): Promotes linear scalability and memcached key/value data storage.
- [MongoDB](https://www.mongodb.com/): Utilizes JSON-like documents and handles large volume, diverse data storage (e.g., e-mails, scanned documents).
- [Redis](https://redis.io/): Popular as a message broker and distributed cache, supporting low-latency reading and writing.
## 2. CRUD Operations
Persistent storage databases have four types of operations that are performed open them, which are commonly abbreviated as *CRUD*:
| CRUD Principle | Popular SQL Statement Keywords |
| :---: | :---: |
| **C**reate | INSERT INTO/VALUES, CREATE TABLE |
| **R**ead | SELECT |
| **U**pdate | UPDATE, ALTER TABLE/ADD |
| **D**elete | DELETE, DROP TABLE |
## 3. Database Terms
**Table:** A database object/structure containing related fields (columns) and their associated records (rows).
**Field:** A column from a database table. This is a vertical data unit with a name and a data type (e.g., Integer, String, Date).
**Record:** A row from a database table. This is a horizontal data unit that spans all of the fields (columns) in a table.
**Entity:** A 'noun' (person, place, or thing) that the data of a record (row) describes.
**Primary Key:** One or more fields (columns) in a database table that uniquely identifies a row by not permitting repeat values (IDs, such as student and employee IDs, are popular primary keys).
**Foreign Key:** One of more fields (columns) in a database table that only include values corresponding to the primary key of another table. Primary and foreign keys, in tandem, define table relationships.
**Referential Integrity:** Occurs when the values of a foreign key successfully correspond to the row values of an associated table's primary key.
**Relational:** A database type in which the relationships between tables are established via matching/corresponding fields (columns). A software program that provides data persistence for and manages relational databases is referred to as an *RDBMS* (Relational Database Management System).
**Normalization:** A data organization approach in which best practices for data integrity are followed (data are consistent and redundancy is reduced).
## 4. SQL Clauses
Six of the most commonly applied SQL clauses include:
* **SELECT:** Specifies which column(s) results should be returned from.
* **FROM:** Specifies which table(s) results should be returned from.
* **WHERE:** Filters datas based on provided conditions/constraints.
* **GROUP BY:** Brings together rows (as summary rows) that have the same values for specified columns/fields.
* **HAVING:** After aggregate functions are utilized, filters grouped rows according to provided specifications.
* **ORDER BY:** Sorts data in ascending (A-Z, 0-9) or descending (Z-A, 9-0) order.
## 5. SQL Constraints
(TODO)
## 6. SQL Filtering and Sorting
(TODO)
## 7. SQL Joins
An SQL `JOIN` clause combines rows/records from multiple tables, relying on a related column/field from between them in doing so. Types of joins include:
**INNER JOIN**: Retrieves records with corresponding values from the tables expressed in the join clause.
**LEFT OUTER JOIN**: Retrieves all records from the 'left' table, as well as corresponding records from the 'right' table.
**RIGHT OUTER JOIN**: Retrieves all records from the 'right' table, as well as the corresponding records from the 'left' table.
**FULL OUTER JOIN**: Retrieves all corresponding records, regardless of if the match is form the 'left' or 'right' table.
## 8. Supplemental Resources
* *[Data Repositories Overview Guide](https://github.com/chaseofthejungle/data-repositories-overview)*
* *[Types of Databases Guide](https://github.com/chaseofthejungle/types-of-databases)*
* *[Codecademy Learn SQL Course](https://www.codecademy.com/learn/learn-sql)*