自己写：拆完拼回去，一行不能差

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这一节的收官：把三张表连回去，和宽表逐行对比，确认信息一点没丢。输出三个数：拼出来几行、宽表几行、内容是否完全一致（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

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← 自己写：把学生信息也搬出去怎么判断一条关系是几对几 →

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代码编辑器

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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)])
def norm(rows):
    return sorted("|".join(str(x) for x in r) for r in rows)

# TODO: 把三张表连起来，取出「学生 电话 课程 老师 教室」五列
joined = db.execute("SELECT  FROM enroll e "
                    "JOIN student s ON s.id = e.student_id "
                    "JOIN course c ON c.id = e.course_id").fetchall()

flat = db.execute("SELECT student, phone, course, teacher, room "
                  "FROM enroll_flat").fetchall()
print(str(len(joined)) + "/" + str(len(flat)) + "/"
      + ("一致" if norm(joined) == norm(flat) else "不一致"))

本次输入：

输出：

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