Transaksi atomik

Telusuri kode sebelum menjalankan

Python · contoh konsep yang dapat dijalankan

from support import database
with database() as con:
    con.execute("CREATE TABLE books(id INTEGER PRIMARY KEY, title TEXT NOT NULL, stock INTEGER CHECK(stock>=0))")
    con.executemany("INSERT INTO books VALUES(?,?,?)", [(1, "Sains", 1), (2, "Seni", 2)])
    con.commit()
    con.execute("CREATE TABLE loans(id INTEGER PRIMARY KEY, borrower TEXT NOT NULL)")
    try:
        with con:
            con.execute("UPDATE books SET stock=stock-1 WHERE id=1 AND stock>0")
            con.execute("INSERT INTO loans(borrower) VALUES(?)", ([None, "Penguji A"][variant],))
    except Exception as error:
        import sqlite3
        if not isinstance(error, sqlite3.IntegrityError):
            raise
    value = [con.execute("SELECT stock FROM books WHERE id=1").fetchone()[0], con.execute("SELECT COUNT(*) FROM loans").fetchone()[0]]

Potongan konsep dari latihan.py · variant 0 = A · variant 1 = B