6.21. SQL Select Subquery — Python
IN (SELECT ...)- subquery
6.21.1. Subqueries
SELECT * FROM astronauts WHERE agency IN ( SELECT name FROM agencies);
SELECT * FROM astronauts WHERE career IN ( SELECT name FROM job_names);
SELECT * FROM logs WHERE level in ( SELECT level FROM logs GROUP BY level HAVING COUNT(*) > 5 );
6.21.2. Assignments
# %% About # - Name: Database Subquery In # - Difficulty: easy # - Lines: 2 # - Minutes: 3 # %% 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 # %% English # 1. Write SQL query to select data: # - table: `users` # - columns: `firstname`, `lastname` # - where: has 2 or more members # - use: subquery # 2. Run doctests - all must succeed # %% Polish # 1. Napisz zapytanie SQL aby wybrać dane: # - tabela: `users` # - kolumny: `firstname`, `lastname` # - gdzie: mająca 2 lub więcej członków # - użyj: podzapytania # 2. Uruchom doctesty - wszystkie muszą się powieść # %% Doctests """ >>> 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': 'Mark', 'lastname': 'Watney'}, {'firstname': 'Melissa', 'lastname': 'Lewis'}, {'firstname': 'Rick', 'lastname': 'Martinez'}, {'firstname': 'Beth', 'lastname': 'Johanssen'}, {'firstname': 'Chris', 'lastname': 'Beck'}] """ # %% Run # - PyCharm: right-click in the editor and `Run Doctest in ...` # - PyCharm: keyboard shortcut `Control + Shift + F10` # - Terminal: `python -m doctest -f -v myfile.py` # %% Imports # %% Types result: str # %% Data # %% Result result = """ SELECT `firstname`, `lastname` FROM `users` WHERE `group` """
# %% About # - Name: Database Subquery CTE # - Difficulty: easy # - Lines: 2 # - Minutes: 3 # %% 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 # %% English # 1. Write SQL query to select data: # - table: `users` # - columns: `firstname`, `lastname` # - where: has 2 or more members # - use: CTE - Common Table Expression # 2. Run doctests - all must succeed # %% Polish # 1. Napisz zapytanie SQL aby wybrać dane: # - tabela: `users` # - kolumny: `firstname`, `lastname` # - gdzie: mająca 2 lub więcej członków # - użyj: CTE - Common Table Expression # 2. Uruchom doctesty - wszystkie muszą się powieść # %% Doctests """ >>> 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': 'Mark', 'lastname': 'Watney'}, {'firstname': 'Melissa', 'lastname': 'Lewis'}, {'firstname': 'Rick', 'lastname': 'Martinez'}, {'firstname': 'Beth', 'lastname': 'Johanssen'}, {'firstname': 'Chris', 'lastname': 'Beck'}] """ # %% Run # - PyCharm: right-click in the editor and `Run Doctest in ...` # - PyCharm: keyboard shortcut `Control + Shift + F10` # - Terminal: `python -m doctest -f -v myfile.py` # %% Imports # %% Types result: str # %% Data # %% Result result = """ SELECT `firstname`, `lastname` FROM `users` WHERE `group` IN ( SELECT `group` FROM `users` GROUP BY `group` HAVING COUNT(`group`) >= 2 ) """