2024-09-30 10:22:19 +02:00

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obj	website	repo
application	https://www.postgresql.org	https://git.postgresql.org/gitweb/?p=postgresql.git

Postgres

PostgreSQL is an advanced, open-source, object-relational database management system. It is renowned for its scalability, reliability, and compliance with the SQL standard. PostgreSQL supports both SQL (relational) and JSON (non-relational) querying, making it highly versatile.

Extensions

PostgreSQL can be extended via extensions:

TimescaleDB - Time-series data
pgVector - Vector database functions
PostGIS - Spatial data

psql

psql is a terminal-based front end to PostgreSQL. It allows users to interact with PostgreSQL databases by executing SQL queries, managing database objects, and performing administrative tasks.

To start psql, open your terminal or command prompt and type:

psql

Connecting to a Database

You can specify the database name, user, host, and port when launching psql:

psql -d database_name -U username -h hostname -p port

Alternatively, you can use environment variables:

export PGDATABASE=mydb
export PGUSER=myuser
export PGPASSWORD=mypassword
export PGHOST=localhost
export PGPORT=5432

psql

Listing Databases and Tables

List Databases:
```
\l
```
List Tables in the Current Database:
```
\dt
```
List All Schemas:
```
\dn
```

Creating and Dropping Databases/Tables

Create a Database:
```
CREATE DATABASE mydb;
```
Drop a Database:
```
DROP DATABASE mydb;
```

Create a Table:

CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    username VARCHAR(50) NOT NULL,
    email VARCHAR(100) NOT NULL
);

Drop a Table:
```
DROP TABLE users;
```

Running SQL Queries

Execute standard SQL commands to interact with your data.

Example: Inserting Data

INSERT INTO users (username, email) VALUES ('john_doe', 'john@example.com');

Example: Querying Data

SELECT * FROM users;

Example: Updating Data

UPDATE users SET email = 'john.doe@example.com' WHERE username = 'john_doe';

Example: Deleting Data

DELETE FROM users WHERE username = 'john_doe';

Meta-Commands

psql provides a set of meta-commands (prefixed with \) that facilitate various tasks.

Common Meta-Commands

Help on Meta-Commands:
```
\?
```
Help on SQL Commands:
```
\h
```
Describe a Table:
```
\d table_name
```
List All Tables, Views, and Sequences:
```
\dt
```
List All Indexes:
```
\di
```
Exit psql:
```
\q
```

Data Types

1. Numeric Types

Small Integer Types
- SMALLINT (2 bytes): Range from -32,768 to +32,767
Integer Types
- INTEGER or INT (4 bytes): Range from -2,147,483,648 to +2,147,483,647
Big Integer Types
- BIGINT (8 bytes): Range from -9,223,372,036,854,775,808 to +9,223,372,036,854,775,807
Decimal/Exact Types
- DECIMAL or NUMERIC (variable size): User-defined precision and scale
Floating-Point Types
- REAL (4 bytes): Single precision floating-point number
- DOUBLE PRECISION (8 bytes): Double precision floating-point number
Serial Types (Auto-Incrementing)
- SERIAL (4 bytes): Auto-incrementing integer (small range)
- BIGSERIAL (8 bytes): Auto-incrementing integer (large range)
- SMALLSERIAL (2 bytes): Auto-incrementing integer (smaller range)

2. Monetary Type

MONEY: Stores currency amounts with a fixed fractional precision

3. Character Types

Fixed-Length Strings
- CHAR(n) or CHARACTER(n): Fixed length (padded with spaces)
Variable-Length Strings
- VARCHAR(n) or CHARACTER VARYING(n): Variable length with a limit
Text
- TEXT: Variable length with no specific limit

4. Binary Data Types

Binary Large Object
- BYTEA: Stores binary strings (byte arrays)

5. Date/Time Types

Date and Time
- DATE: Calendar date (year, month, day)
- TIME (no time zone): Time of day (without time zone)
- TIMETZ (with time zone): Time of day (with time zone)
- TIMESTAMP (no time zone): Date and time without time zone
- TIMESTAMPTZ (with time zone): Date and time with time zone
Intervals
- INTERVAL: Time span (e.g., days, months, hours)

6. Boolean Type

BOOLEAN: Stores TRUE, FALSE, or NULL

7. UUID Type

UUID: Stores Universally Unique Identifiers (128-bit values)

8. Enumerated Types

ENUM: User-defined enumerated type (a static set of values)

9. Geometric Types

POINT: Stores a geometric point (x, y)
LINE: Infinite line
LSEG: Line segment
BOX: Rectangular box
PATH: Geometric path (multiple points)
POLYGON: Closed geometric figure
CIRCLE: Circle

10. Network Address Types

CIDR: IPv4 or IPv6 network block
INET: IPv4 or IPv6 address
MACADDR: MAC address
MACADDR8: MAC address (EUI-64 format)

11. Bit String Types

Fixed-Length Bit Strings
- BIT(n): Fixed-length bit string
Variable-Length Bit Strings
- BIT VARYING(n): Variable-length bit string

12. Text Search Types

TSVECTOR: Text search document
TSQUERY: Text search query

13. JSON Types

JSON: Textual JSON data
JSONB: Binary JSON data (more efficient for indexing)

14. Array Types

ARRAY: Allows any data type to be stored as an array (e.g., INTEGER[], TEXT[])

15. Range Types

INT4RANGE: Range of INTEGER
INT8RANGE: Range of BIGINT
NUMRANGE: Range of NUMERIC
TSRANGE: Range of TIMESTAMP WITHOUT TIME ZONE
TSTZRANGE: Range of TIMESTAMP WITH TIME ZONE
DATERANGE: Range of DATE

16. Composite Types

User-defined types that consist of multiple fields of various types

17. Object Identifier Types (OID)

OID: Object identifier (used internally by PostgreSQL)
REGCLASS, REGPROC, REGTYPE: Special types for referencing classes, procedures, and types by OID or name

18. Pseudo-Types

ANY: Accepts any data type
ANYARRAY: Accepts any array data type
ANYELEMENT: Represents any type of element
ANYENUM: Accepts any ENUM type
ANYNONARRAY: Any non-array type
VOID: No data (used with functions that return no value)
TRIGGER: Used in triggers
LANGUAGE_HANDLER: Used internally for language support

Docker-Compose

services:
  postgres:
    image: postgres:17
    container_name: postgres
    environment:
      POSTGRES_USER: myuser
      POSTGRES_PASSWORD: mypassword
      POSTGRES_DB: mydb
    ports:
      - "5432:5432"
    volumes:
      - ./postgres:/var/lib/postgresql/data
    restart: always

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