6.13. SQL Select Limit

6.13.1. Limit Results

SELECT *
FROM astronauts
LIMIT 5;

6.13.2. Pagination

SELECT *
FROM astronauts
LIMIT 0, 10;

SELECT *
FROM astronauts
LIMIT 10, 10;

SELECT *
FROM astronauts
LIMIT 20, 10;

6.13.3. Assignments

# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -v myfile.py`

# %% About
# - Name: Database Select Limit
# - Difficulty: easy
# - Lines: 2
# - Minutes: 3

# %% English
# 1. Write SQL query to select data:
#    - table: `users`
#    - columns: `firstname`, `lastname`
#    - limit: 3
# 2. Run doctests - all must succeed

# %% Polish
# 1. Napisz zapytanie SQL aby wybrać dane:
#    - tabela: `users`
#    - kolumny: `firstname`, `lastname`
#    - limit: 3
# 2. Uruchom doctesty - wszystkie muszą się powieść

# %% Tests
"""
>>> import sys; sys.tracebacklimit = 0
>>> from pprint import pprint
>>> from pathlib import Path
>>> import sqlite3

>>> database = Path(__file__).parent.parent / 'shop.db'
>>> with sqlite3.connect(database) as db:
...    db.row_factory = sqlite3.Row
...    data = map(dict, db.execute(result).fetchall())

>>> pprint(list(data), sort_dicts=False, width=79)
[{'firstname': 'Chris', 'lastname': 'Beck'},
 {'firstname': 'Beth', 'lastname': 'Johanssen'},
 {'firstname': 'Melissa', 'lastname': 'Lewis'}]
"""

# Write SQL query to select data:
# - table: `users`
# - columns: `firstname`, `lastname`
# - limit: 3
# type: str
result = """

SELECT `firstname`, `lastname`
FROM `users`

"""

# FIXME: zmienić offset aby było widać różnicę między limit

# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -v myfile.py`

# %% About
# - Name: Database Select Offset
# - Difficulty: easy
# - Lines: 2
# - Minutes: 3

# %% English
# 1. Write SQL query to select data:
#    - table: `users`
#    - columns: `firstname`, `lastname`
#    - limit: 3
#    - offset: 3
# 2. Run doctests - all must succeed

# %% Polish
# 1. Napisz zapytanie SQL aby wybrać dane:
#    - tabela: `users`
#    - kolumny: `firstname`, `lastname`
#    - limit: 3
#    - przesunięcie: 3
# 2. Uruchom doctesty - wszystkie muszą się powieść

# %% Tests
"""
>>> import sys; sys.tracebacklimit = 0
>>> from pprint import pprint
>>> from pathlib import Path
>>> import sqlite3

>>> database = Path(__file__).parent.parent / 'shop.db'
>>> with sqlite3.connect(database) as db:
...    db.row_factory = sqlite3.Row
...    data = map(dict, db.execute(result).fetchall())

>>> pprint(list(data), sort_dicts=False, width=79)
[{'firstname': 'Rick', 'lastname': 'Martinez'},
 {'firstname': 'Alex', 'lastname': 'Vogel'},
 {'firstname': 'Mark', 'lastname': 'Watney'}]
"""

# Write SQL query to select data:
# - table: `users`
# - columns: `firstname`, `lastname`
# - limit: 3
# - offset: 3
# type: str
result = """

SELECT `firstname`, `lastname`
FROM `users`
LIMIT 3

"""