dataset/medium_cases.json

[
  {
    "id": "medium_001",
    "category": "logic",
    "description": "Fix the wrong JOIN type: INNER JOIN excludes users with no orders. Should be LEFT JOIN to include all users.",
    "buggy_query": "SELECT u.id, u.name, COUNT(o.id) as order_count FROM users u INNER JOIN orders o ON u.id = o.user_id GROUP BY u.id, u.name",
    "fixed_query": "SELECT u.id, u.name, COUNT(o.id) as order_count FROM users u LEFT JOIN orders o ON u.id = o.user_id GROUP BY u.id, u.name",
    "error_message": "No error thrown — query runs but returns wrong results (missing users with 0 orders)",
    "database_schema": {
      "users":  ["id INT PRIMARY KEY", "name VARCHAR(100)", "email VARCHAR(100)"],
      "orders": ["id INT PRIMARY KEY", "user_id INT REFERENCES users(id)", "total DECIMAL", "status VARCHAR(20)"]
    },
    "expected_output": [
      {"id": 1, "name": "Alice", "order_count": 3},
      {"id": 2, "name": "Bob",   "order_count": 0},
      {"id": 3, "name": "Carol", "order_count": 1}
    ],
    "actual_buggy_output": [
      {"id": 1, "name": "Alice", "order_count": 3},
      {"id": 3, "name": "Carol", "order_count": 1}
    ],
    "error_type": "logic",
    "error_location": "JOIN type",
    "fix_description": "Change INNER JOIN to LEFT JOIN so users with zero orders are included",
    "estimated_fix_steps": 3,
    "partial_credit_hints": {
      "identifies_missing_rows": 0.15,
      "identifies_join_type_issue": 0.2,
      "correct_join_fix": 0.4,
      "explanation": 0.15,
      "confidence": 0.1
    }
  },
  {
    "id": "medium_002",
    "category": "logic",
    "description": "Fix the wrong JOIN condition: joining on wrong column causes cartesian-like explosion of results.",
    "buggy_query": "SELECT o.id, o.total, p.name FROM orders o JOIN order_items oi ON o.id = oi.order_id JOIN products p ON oi.id = p.id",
    "fixed_query": "SELECT o.id, o.total, p.name FROM orders o JOIN order_items oi ON o.id = oi.order_id JOIN products p ON oi.product_id = p.id",
    "error_message": "No error thrown — query runs but returns incorrect product associations",
    "database_schema": {
      "orders":      ["id INT PRIMARY KEY", "user_id INT", "total DECIMAL"],
      "order_items": ["id INT PRIMARY KEY", "order_id INT", "product_id INT", "quantity INT"],
      "products":    ["id INT PRIMARY KEY", "name VARCHAR(100)", "price DECIMAL"]
    },
    "expected_output": [
      {"id": 101, "total": 250.00, "name": "Laptop"},
      {"id": 102, "total": 89.99,  "name": "Mouse"}
    ],
    "error_type": "logic",
    "error_location": "Second JOIN condition — oi.id should be oi.product_id",
    "fix_description": "Change ON oi.id = p.id to ON oi.product_id = p.id",
    "estimated_fix_steps": 3,
    "partial_credit_hints": {
      "identifies_wrong_column": 0.2,
      "identifies_join_condition": 0.2,
      "correct_fix": 0.4,
      "explanation": 0.15,
      "confidence": 0.05
    }
  },
  {
    "id": "medium_003",
    "category": "logic",
    "description": "Fix the aggregation logic: HAVING clause filters before GROUP BY aggregation is complete, wrong column used.",
    "buggy_query": "SELECT department, AVG(salary) as avg_salary FROM employees WHERE AVG(salary) > 70000 GROUP BY department",
    "fixed_query": "SELECT department, AVG(salary) as avg_salary FROM employees GROUP BY department HAVING AVG(salary) > 70000",
    "error_message": "ERROR: aggregate functions are not allowed in WHERE",
    "database_schema": {
      "employees": ["id INT PRIMARY KEY", "name VARCHAR(100)", "department VARCHAR(50)", "salary DECIMAL"]
    },
    "expected_output": [
      {"department": "Engineering", "avg_salary": 95000.00},
      {"department": "Data Science","avg_salary": 88000.00}
    ],
    "error_type": "logic",
    "error_location": "WHERE clause — aggregate function used in WHERE instead of HAVING",
    "fix_description": "Move AVG(salary) > 70000 from WHERE to HAVING clause, placed after GROUP BY",
    "estimated_fix_steps": 3,
    "partial_credit_hints": {
      "identifies_where_vs_having": 0.2,
      "identifies_aggregate_misuse": 0.2,
      "correct_fix": 0.4,
      "explanation": 0.15,
      "confidence": 0.05
    }
  },
  {
    "id": "medium_004",
    "category": "logic",
    "description": "Fix the subquery logic: correlated subquery compares wrong column, returning incorrect filtered set.",
    "buggy_query": "SELECT id, name, salary FROM employees e WHERE salary > (SELECT AVG(salary) FROM employees WHERE department = e.id)",
    "fixed_query": "SELECT id, name, salary FROM employees e WHERE salary > (SELECT AVG(salary) FROM employees WHERE department = e.department)",
    "error_message": "No error thrown — returns incorrect rows because subquery correlates on wrong column",
    "database_schema": {
      "employees": ["id INT PRIMARY KEY", "name VARCHAR(100)", "department VARCHAR(50)", "salary DECIMAL"]
    },
    "expected_output": [
      {"id": 3, "name": "Carol", "salary": 110000},
      {"id": 7, "name": "Dave",  "salary": 98000}
    ],
    "error_type": "logic",
    "error_location": "Correlated subquery WHERE clause — e.id should be e.department",
    "fix_description": "Change WHERE department = e.id to WHERE department = e.department",
    "estimated_fix_steps": 4,
    "partial_credit_hints": {
      "identifies_correlated_subquery": 0.15,
      "identifies_wrong_correlation": 0.2,
      "correct_fix": 0.45,
      "explanation": 0.15,
      "confidence": 0.05
    }
  },
  {
    "id": "medium_005",
    "category": "logic",
    "description": "Fix the DISTINCT misuse: DISTINCT applied to wrong scope, counting duplicates incorrectly.",
    "buggy_query": "SELECT COUNT(DISTINCT *) FROM orders WHERE status = 'completed'",
    "fixed_query": "SELECT COUNT(DISTINCT id) FROM orders WHERE status = 'completed'",
    "error_message": "ERROR: COUNT(DISTINCT) with multiple columns requires explicit column list",
    "database_schema": {
      "orders": ["id INT PRIMARY KEY", "user_id INT", "total DECIMAL", "status VARCHAR(20)"]
    },
    "expected_output": [{"count": 47}],
    "error_type": "logic",
    "error_location": "COUNT(DISTINCT *) — wildcard not valid with DISTINCT",
    "fix_description": "Replace COUNT(DISTINCT *) with COUNT(DISTINCT id) to count unique order IDs",
    "estimated_fix_steps": 2,
    "partial_credit_hints": {
      "identifies_distinct_misuse": 0.25,
      "correct_fix": 0.5,
      "explanation": 0.15,
      "confidence": 0.1
    }
  }
]