From 85792613b534c40183c1cc135311546582e86a5b Mon Sep 17 00:00:00 2001
From: jay817 <jaewooklee.dev@gmail.com>
Date: Sat, 21 Sep 2024 22:03:11 -0400
Subject: [PATCH] Add sqlite3-python/README.md

---
 sqlite3-python/README.md | 113 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 113 insertions(+)
 create mode 100644 sqlite3-python/README.md

diff --git a/sqlite3-python/README.md b/sqlite3-python/README.md
new file mode 100644
index 0000000..4f73506
--- /dev/null
+++ b/sqlite3-python/README.md
@@ -0,0 +1,113 @@
+```python
+class SQL:
+    def __init__(self, filename='db.sqlite'):
+        import sqlite3
+        self.conn = sqlite3.connect(filename, 
+            isolation_level=None # autocommit mode: ON
+        )
+        self('PRAGMA journal_mode=WAL;') # WAL mode: ON
+        self.conn.row_factory = lambda *args: dict(sqlite3.Row(*args))
+
+    def __call__(self, *args):
+        import pandas as pd
+        return pd.DataFrame(self.conn.execute(*args))
+
+    def __getattr__(self, table):
+        return self(f"SELECT * FROM {table}")
+
+    def __repr__(self):
+        return self("SELECT name FROM sqlite_master WHERE type='table'").to_string()
+```
+
+```python
+#
+try: get_ipython()
+except: display = print
+
+sql = SQL()
+sql
+
+#
+# 학생 테이블 생성
+sql('''CREATE TABLE IF NOT EXISTS students 
+       (id INTEGER PRIMARY KEY, name TEXT, age INTEGER, grade INTEGER)''')
+
+# 과목 테이블 생성
+sql('''CREATE TABLE IF NOT EXISTS courses 
+       (id INTEGER PRIMARY KEY, name TEXT, professor TEXT)''')
+
+# 수강 테이블 생성 (학생과 과목의 관계)
+sql('''CREATE TABLE IF NOT EXISTS enrollments 
+       (student_id INTEGER, course_id INTEGER, 
+        FOREIGN KEY(student_id) REFERENCES students(id), 
+        FOREIGN KEY(course_id) REFERENCES courses(id))''')
+sql
+
+#
+# 학생 데이터 삽입
+sql('INSERT INTO students (name, age, grade) VALUES (?, ?, ?)', ('김철수', 20, 2))
+sql('INSERT INTO students (name, age, grade) VALUES (?, ?, ?)', ('이영희', 22, 4))
+sql('INSERT INTO students (name, age, grade) VALUES (?, ?, ?)', ('박민수', 19, 1))
+
+# 과목 데이터 삽입
+sql('INSERT INTO courses (name, professor) VALUES (?, ?)', ('데이터베이스', '홍길동'))
+sql('INSERT INTO courses (name, professor) VALUES (?, ?)', ('알고리즘', '이순신'))
+sql('INSERT INTO courses (name, professor) VALUES (?, ?)', ('인공지능', '강감찬'))
+
+# 수강 데이터 삽입
+sql('INSERT INTO enrollments (student_id, course_id) VALUES (?, ?)', (1, 1))
+sql('INSERT INTO enrollments (student_id, course_id) VALUES (?, ?)', (1, 2))
+sql('INSERT INTO enrollments (student_id, course_id) VALUES (?, ?)', (2, 2))
+sql('INSERT INTO enrollments (student_id, course_id) VALUES (?, ?)', (3, 3))
+
+print("Students:")
+display(sql.students)
+print("\nCourses:")
+display(sql.courses)
+print("\nEnrollments:")
+display(sql.enrollments)
+
+#
+# JOIN을 사용하여 학생별 수강 과목 조회
+print("\n학생별 수강 과목:")
+enrollments_df = sql('''
+    SELECT students.name AS student_name, courses.name AS course_name
+    FROM students
+    JOIN enrollments ON students.id = enrollments.student_id
+    JOIN courses ON enrollments.course_id = courses.id
+''')
+display(enrollments_df)
+
+#
+# 특정 과목을 수강하는 학생 수 조회
+course_name = '알고리즘'
+result = sql('''
+    SELECT COUNT(*) as student_count
+    FROM enrollments
+    JOIN courses ON enrollments.course_id = courses.id
+    WHERE courses.name = ?
+''', (course_name,))
+print(f"\n'{course_name}' 과목을 수강하는 학생 수: {result['student_count'].iloc[0]}")
+
+#
+# 가장 많은 학생이 수강하는 과목 조회
+most_popular_course = sql('''
+    SELECT courses.name, COUNT(*) as enrollment_count
+    FROM enrollments
+    JOIN courses ON enrollments.course_id = courses.id
+    GROUP BY courses.id
+    ORDER BY enrollment_count DESC
+    LIMIT 1
+''')
+print(f"\n가장 인기 있는 과목: {most_popular_course['name'].iloc[0]} (수강생 {most_popular_course['enrollment_count'].iloc[0]}명)")
+
+#
+# 최종 상태 출력
+print("\n최종 상태:")
+print("Students:")
+display(sql('SELECT * FROM students'))
+print("\nCourses:")
+display(sql('SELECT * FROM courses'))
+print("\nEnrollments:")
+display(sql('SELECT * FROM enrollments'))
+```
\ No newline at end of file