⚠️ 漏改一行，同一门课有了两个老师

在宽表上改老师，故意漏掉一行。输出两个数：改了几行、现在"数学"这门课有几种老师（用 / 隔开）。

enroll_flat（一张宽表，什么都塞在里面）
student  phone  course  teacher  room
阿岚     111    数学    王老师   A101
阿岚     111    英语    李老师   B202
小满     222    数学    王老师   A101
阿泰     333    英语    李老师   B202
小满     222    物理    张老师   C303
南风     444    数学    王老师   A101

拆开之后的三张
student(id, name, phone)          4 行
course (id, name, teacher, room)  3 行
enroll (student_id, course_id)    6 行

import sqlite3
db = sqlite3.connect(":memory:")
db.executescript("""
CREATE TABLE enroll_flat (student TEXT, phone TEXT, course TEXT, teacher TEXT, room TEXT);
CREATE TABLE student (id INTEGER PRIMARY KEY, name TEXT NOT NULL UNIQUE, phone TEXT NOT NULL);
CREATE TABLE course  (id INTEGER PRIMARY KEY, name TEXT NOT NULL UNIQUE,
                      teacher TEXT NOT NULL, room TEXT NOT NULL);
CREATE TABLE enroll  (student_id INTEGER, course_id INTEGER,
                      PRIMARY KEY (student_id, course_id));
""")
db.executemany("INSERT INTO enroll_flat VALUES (?,?,?,?,?)", [
    ("阿岚", "111", "数学", "王老师", "A101"),
    ("阿岚", "111", "英语", "李老师", "B202"),
    ("小满", "222", "数学", "王老师", "A101"),
    ("阿泰", "333", "英语", "李老师", "B202"),
    ("小满", "222", "物理", "张老师", "C303"),
    ("南风", "444", "数学", "王老师", "A101")])
db.executemany("INSERT INTO student VALUES (?,?,?)", [
    (1, "阿岚", "111"), (2, "小满", "222"), (3, "阿泰", "333"), (4, "南风", "444")])
db.executemany("INSERT INTO course VALUES (?,?,?,?)", [
    (1, "数学", "王老师", "A101"), (2, "英语", "李老师", "B202"),
    (3, "物理", "张老师", "C303")])
db.executemany("INSERT INTO enroll VALUES (?,?)", [
    (1, 1), (1, 2), (2, 1), (3, 2), (2, 3), (4, 1)])
a = db.execute("UPDATE enroll_flat SET teacher = '赵老师' "
               "WHERE course = '数学' AND student <> '南风'").rowcount
b = db.execute("SELECT COUNT(DISTINCT teacher) FROM enroll_flat "
               "WHERE course = '数学'").fetchone()[0]
print(str(a) + "/" + str(b))