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https://github.com/ahmedosamamath/postgresql-basics
A beginner-friendly guide to PostgreSQL covering installation, basic commands, SQL queries, and database management techniques.
https://github.com/ahmedosamamath/postgresql-basics
postgres postgresql postgresql-database sql
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A beginner-friendly guide to PostgreSQL covering installation, basic commands, SQL queries, and database management techniques.
- Host: GitHub
- URL: https://github.com/ahmedosamamath/postgresql-basics
- Owner: AhmedOsamaMath
- License: mit
- Created: 2024-09-19T09:06:07.000Z (2 months ago)
- Default Branch: main
- Last Pushed: 2024-09-20T03:02:33.000Z (about 2 months ago)
- Last Synced: 2024-11-04T05:30:32.923Z (15 days ago)
- Topics: postgres, postgresql, postgresql-database, sql
- Homepage:
- Size: 43.9 KB
- Stars: 6
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# PostgreSQL Basics
This repository contains an overview of basic PostgreSQL commands, installation steps, and common SQL queries. PostgreSQL is a powerful, open-source object-relational database system with a strong reputation for reliability and performance.
## Table of Contents
1. [Download and Install PostgreSQL](#download-and-install-postgresql)
2. [Add PostgreSQL to PATH](#add-postgresql-to-path-for-windows)
3. [Create Shortcuts for pgAdmin and psql Shell](#create-shortcuts-for-pgadmin-and-psql-shell)
4. [Basic PostgreSQL Commands](#basic-postgresql-commands)
5. [User and Role Management](#user-and-role-management)
6. [Database Management](#database-management)
7. [Data Types](#data-types)
8. [Table Management](#table-management)
9. [Data Manipulation](#data-manipulation)
10. [Query Clauses](#query-clauses)
11. [Indexes and Constraints](#indexes-and-constraints)
12. [Transactions](#transactions)
13. [Backup and Restore](#backup-and-restore)
14. [Advanced Queries](#advanced-queries)
## Download and Install PostgreSQL
1. Visit the official [PostgreSQL Downloads](https://www.postgresql.org/download/) page.
2. Select your operating system (Windows, macOS, or Linux).
3. Follow the installation steps provided by the PostgreSQL installer.
## Add PostgreSQL to PATH (for Windows)
1. After installation, locate the PostgreSQL installation directory (usually in `C:\Program Files\PostgreSQL\version\bin`).
2. Add this path to the system's environment variables:
- Open "System Properties" (Right-click `This PC` → `Properties` → `Advanced system settings`).
- Under "System Properties" → `Advanced` → Click `Environment Variables`.
- In the "System Variables" section, find `Path` and click `Edit`.
- Add the PostgreSQL `bin` folder to the path, and click `OK`.
## Create Shortcuts for pgAdmin and psql Shell
- **For pgAdmin (GUI):**
1. Locate `pgAdmin 4` in your installed programs or the PostgreSQL folder.
2. Right-click on the program → `Send to` → `Desktop (create shortcut)`.
- **For psql Shell (CLI):**
1. Find the `SQL Shell (psql)` in the PostgreSQL directory or Start menu.
2. Right-click on it → `Send to` → `Desktop (create shortcut)`.
## Basic PostgreSQL Commands
- **Connect to a Database:**
```bash
psql -U username -d dbname
```
Once connected, type `help` for help:
```
You are using psql, the command-line interface to PostgreSQL.
Type: \copyright for distribution terms
\h for help with SQL commands
\? for help with psql commands
\g or terminate with semicolon to execute query
\q to quit
```
- **Get help for psql commands before connecting:**
```bash
psql --help
```
This displays a list of available options and their descriptions, such as:
- `-U username` to specify the user.
- `-d dbname` to connect to a specific database.
- `-h host` to connect to a specific host.
- `-p port` to specify the port number.
## User and Role Management
- **Create User:**
```sql
CREATE USER username WITH PASSWORD 'password';
```
- **Grant Superuser Privileges:**
```sql
ALTER USER username WITH SUPERUSER;
```
- **Grant User Privileges:**
```sql
GRANT ALL PRIVILEGES ON DATABASE dbname TO username;
```
- **List Users:**
```sql
\du
\du+ -- for more details
```
- **Delete User:**
```sql
DROP USER username;
```
## Database Management
- **Create Database:**
```sql
CREATE DATABASE dbname;
```
- **Switch to Another Database:**
```sql
\c dbname
```
- **List Databases:**
```sql
\l
```
- **Delete Database:**
```sql
DROP DATABASE dbname;
```
- **Execute SQL Script from a File:**
```sql
\i /path/to/file.sql
```
## Data Types
| Data Type | Description |
|-------------------|------------------------------------------------------|
| `INTEGER` | Stores whole numbers |
| `SERIAL` | Auto-incrementing integer |
| `BIGINT` | Stores large whole numbers |
| `NUMERIC(p, s)` | Stores exact numbers with precision and scale |
| `REAL` | Stores floating-point numbers |
| `DOUBLE PRECISION`| Stores double precision floating-point numbers |
| `VARCHAR(n)` | Stores variable-length text, up to `n` characters |
| `TEXT` | Stores variable-length text (unlimited) |
| `BOOLEAN` | Stores `TRUE` or `FALSE` |
| `DATE` | Stores a date (year, month, day) |
| `TIMESTAMP` | Stores both date and time |
| `UUID` | Stores universally unique identifiers |
## Table Management
- **Create a Table with `PRIMARY KEY` and `NOT NULL`:**
```sql
CREATE TABLE tablename (
id SERIAL PRIMARY KEY,
column1 VARCHAR(255) NOT NULL,
column2 INTEGER NOT NULL,
column3 DATE
);
```
- **View Table Schema:**
```sql
\d tablename
```
## Data Manipulation
- **Insert Data:**
```sql
INSERT INTO tablename (column1, column2) VALUES (value1, value2);
```
- **Update Data:**
```sql
UPDATE tablename SET column1 = value1 WHERE condition;
```
- **Delete Data:**
```sql
DELETE FROM tablename WHERE condition;
```
- **Select Data:**
```sql
SELECT column1, column2 FROM tablename WHERE condition;
```
- **Using AND, OR conditions in WHERE:**
```sql
SELECT * FROM tablename WHERE condition1 AND (condition2 OR condition3);
```
## Query Clauses
- **LIMIT Clause:**
```sql
SELECT * FROM tablename LIMIT 10;
```
- **OFFSET Clause:**
```sql
SELECT * FROM tablename LIMIT 10 OFFSET 5;
```
- **FETCH Clause:**
```sql
SELECT * FROM tablename OFFSET 5 FETCH NEXT 10 ROWS ONLY;
```
- **IN Clause:**
```sql
SELECT * FROM tablename WHERE column IN ('value1', 'value2', 'value3');
```
- **DISTINCT Clause:**
```sql
SELECT DISTINCT column FROM tablename;
```
- **ORDER BY Clause:**
```sql
SELECT * FROM tablename ORDER BY column ASC; -- Order results in ascending order (default)
SELECT * FROM tablename ORDER BY column DESC; -- Order results in descending order:
```
## Indexes and Constraints
- **Create Index:**
```sql
CREATE INDEX indexname ON tablename (columnname);
```
- **Add Foreign Key:**
```sql
ALTER TABLE tablename ADD CONSTRAINT fk_name FOREIGN KEY (columnname) REFERENCES other_table (columnname);
```
## Transactions
- **Begin Transaction:**
```sql
BEGIN;
```
- **Commit Transaction:**
```sql
COMMIT;
```
- **Rollback Transaction:**
```sql
ROLLBACK;
```
## Backup and Restore
- **Backup a Database:**
```bash
pg_dump dbname > backupfile.sql
```
- **Backup only the schema (pre-data including indexes, sequences, etc.):**
```bash
pg_dump --schema-only dbname > schema_backup.sql
```
- **Restore a Database:**
```bash
psql dbname < backupfile.sql
```
## Advanced Queries
- **Join Tables:**
```sql
SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column;
```
- **Group By:**
```sql
SELECT column, COUNT(*) FROM tablename GROUP BY column;
```