import unittest
import psycopg2
import pandas as pd

class TestPostgresQuery(unittest.TestCase):
    @classmethod
    def setUpClass(cls):
        cls.connection = psycopg2.connect(
            host="localhost",
            user="agent",
            password="qwerty",
            dbname="testdb",
            sslmode="disable"
        )
        cls.cursor = cls.connection.cursor()

    def test_all_columns_present(self):
        """Check if all required columns including salary_band are present in query result."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        columns = [desc[0] for desc in self.cursor.description]
        expected_columns = [
            "id", "name", "department", "salary", "years_at_company", "salary_band"
        ]
        missing_columns = [col for col in expected_columns if col not in columns]
        _dynamic_test(
            self,
            not missing_columns,
            "All required columns including salary_band are present.",
            f"Missing columns: {', '.join(missing_columns)}"
        )

    def test_senior_band(self):
        """Check if salary_band is 'Senior' for salary >= 90000."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        rows = self.cursor.fetchall()
        columns = [desc[0] for desc in self.cursor.description]
        df = pd.DataFrame(rows, columns=columns)
        senior_rows = df[df['salary'] >= 90000]
        incorrect = senior_rows[senior_rows['salary_band'] != 'Senior']
        _dynamic_test(
            self,
            incorrect.empty,
            "All employees with salary >= 90000 are labeled 'Senior'.",
            f"Incorrect salary_band for ids: {incorrect['id'].tolist()} (expected 'Senior')"
        )

    def test_mid_band(self):
        """Check if salary_band is 'Mid' for 60000 <= salary < 90000."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        rows = self.cursor.fetchall()
        columns = [desc[0] for desc in self.cursor.description]
        df = pd.DataFrame(rows, columns=columns)
        mid_rows = df[(df['salary'] >= 60000) & (df['salary'] < 90000)]
        incorrect = mid_rows[mid_rows['salary_band'] != 'Mid']
        _dynamic_test(
            self,
            incorrect.empty,
            "All employees with 60000 <= salary < 90000 are labeled 'Mid'.",
            f"Incorrect salary_band for ids: {incorrect['id'].tolist()} (expected 'Mid')"
        )

    def test_junior_band(self):
        """Check if salary_band is 'Junior' for salary < 60000."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        rows = self.cursor.fetchall()
        columns = [desc[0] for desc in self.cursor.description]
        df = pd.DataFrame(rows, columns=columns)
        junior_rows = df[df['salary'] < 60000]
        incorrect = junior_rows[junior_rows['salary_band'] != 'Junior']
        _dynamic_test(
            self,
            incorrect.empty,
            "All employees with salary < 60000 are labeled 'Junior'.",
            f"Incorrect salary_band for ids: {incorrect['id'].tolist()} (expected 'Junior')"
        )

    def test_salary_band_for_all_rows(self):
        """Check that salary_band is not NULL for any employee."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        rows = self.cursor.fetchall()
        columns = [desc[0] for desc in self.cursor.description]
        df = pd.DataFrame(rows, columns=columns)
        null_bands = df[df['salary_band'].isnull()]
        _dynamic_test(
            self,
            null_bands.empty,
            "salary_band is assigned for every employee.",
            f"salary_band is NULL for ids: {null_bands['id'].tolist()}"
        )

def _dynamic_test(test_case, condition, success_message, failure_message):
    if condition:
        test_case._testMethodName = success_message
        test_case.assertTrue(True, success_message)
    else:
        test_case._testMethodName = failure_message
        test_case.fail(failure_message)

def normalize_text(text):
    text = text.lower()
    text = re.sub(r"\\s{2,}", " ", text)
    text = re.sub(r"\\s*([,:?])\\s*", r"\\1 ", text)
    return text.strip()

if __name__ == "__main__":
    unittest.main()


test_solution.py

SQLにおけるCASE WHEN文を基礎的な条件分岐からデータ分析・レポーティングでの高度な活用例まで習得できる包括的なモジュールです。理論と実践的な課題を通じて、複雑なビジネス要件に対応する表現力豊かなクエリの作成方法を学びます。

CASE WHEN文の基本、構文、およびSQLクエリでの単純な条件付きロジックへの活用方法を学習します。

チャレンジ：部門別給与バンド

解答