import unittest
import psycopg2

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_balance_index_exists(self):
        """Check that the index 'balance_index' exists on 'BankAccounts'."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        self.cursor.execute("""
            SELECT indexname FROM pg_indexes 
            WHERE tablename = 'bankaccounts' AND indexname = 'balance_index';
        """)
        result = self.cursor.fetchone()
        _dynamic_test(
            self,
            result is not None,
            "The index 'balance_index' exists on the 'BankAccounts' table.",
            "The index 'balance_index' does not exist on the 'BankAccounts' table."
        )

    def test_balance_index_column(self):
        """Check that 'balance_index' is created on the 'balance' column."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        self.cursor.execute("""
            SELECT a.attname
            FROM pg_class t
            JOIN pg_index ix ON t.oid = ix.indrelid
            JOIN pg_class i ON i.oid = ix.indexrelid
            JOIN pg_attribute a ON a.attrelid = t.oid AND a.attnum = ANY(ix.indkey)
            WHERE t.relname = 'bankaccounts' AND i.relname = 'balance_index';
        """)
        columns = [row[0] for row in self.cursor.fetchall()]
        condition = 'balance' in columns and len(columns) == 1
        _dynamic_test(
            self,
            condition,
            "The index 'balance_index' is created on the 'balance' column only.",
            "The index 'balance_index' is not correctly created on the 'balance' column."
        )

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

Begin an exciting journey through SQL with Advanced Techniques in SQL. Learn about the important ACID properties that help keep data accurate in database transactions. Discover advanced ways to optimize your queries to improve database performance. Explore special SQL features like window functions, triggers, Data Control Language (DCL), and NoSQL databases. This will help you handle modern database management confidently and effectively.

Now we explore the basic principles of ACID (Atomicity, Consistency, Isolation, Durability) in database management. Learn how these principles ensure reliable transactions by guaranteeing complete operations, keeping data consistent, isolating concurrent transactions, and ensuring permanent data storage.

Explore how to enhance the efficiency of your SQL queries through index optimization. Delve into the significance of indexes in database performance, learning how to design, implement, and utilize them effectively. Discover strategies for choosing the appropriate indexes, understanding their impact on query execution plans, and optimizing query performance through index selection and utilization.

This section explores pivotal topics such as Triggers, Window Functions, and DCL (Data Control Language), offering comprehensive insights into their implementation and optimization strategies. Furthermore, it navigates the landscape of NoSQL DBMS, providing a thorough understanding of its architecture, advantages, and practical applications.

Challenge: Creating B-tree Index

Solution

Challenge: Creating B-tree Index

Solution