# SQL & Excel Interview Prep Guide
## 📸 File History Snapshot (2025-12-05T20:34:53.110Z)
## ◂ USER
  amazon interview quesitons
## ◆ ASSISTANT
  I can help you prepare for Amazon interview questions! Amazon interviews are known for their focus on **Leadership Principles** and **behavioral questions** using the **STAR method** (Situation, Task, Action, Result).
  
  ## Common Amazon Interview Question Categories
  
  ### Leadership Principles-Based Questions
  
  Amazon has 16 Leadership Principles. Here are questions tied to key ones:
  
  **Customer Obsession**
  - Tell me about a time you went above and beyond for a customer
  - Describe a situation where you had to balance customer needs with business constraints
  
  **Ownership**
  - Tell me about a time you took on something outside your area of responsibility
  - Describe a project you owned end-to-end
  
  **Bias for Action**
  - Tell me about a time you made a decision without having all the data
  - Describe a situation where you had to act quickly
  
  **Dive Deep**
  - Tell me about a time you used data to make a decision
  - Describe a situation where you found a root cause others missed
  
  **Deliver Results**
  - Tell me about your most challenging project and how you delivered it
  - Describe a time you had to overcome significant obstacles to meet a goal
  
  **Invent and Simplify**
  - Tell me about a time you created a new process or simplified an existing one
  - Describe an innovative solution you developed
  
  **Learn and Be Curious**
  - Tell me about something new you taught yourself recently
  - Describe how you stay current in your field
  
  ### Technical Questions (for technical roles)
  
  - System design (design Twitter, design a URL shortener, etc.)
  - Coding problems (LeetCode-style, often medium difficulty)
  - SQL queries (for data roles)
  - Architecture discussions
  
  ---
  
  Would you like me to:
  1. **Deep dive into specific Leadership Principles** with sample answers?
  2. **Practice SQL questions** using your MariaDB database?
  3. **Cover system design topics**?
  4. **Go through behavioral question frameworks**?
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## 📸 File History Snapshot (2025-12-05T20:48:58.388Z)
## ◂ USER
  given a table employeeid, employeeFistname, department, supervise_id(this is == employeeid). Question. list employeeFistnmane with department and their supervise firstname
## ◆ ASSISTANT
  This is a classic **self-join** question! You need to join the employee table to itself to match employees with their supervisors.
  
  ## Solution
  
  ```sql
  SELECT 
      e.employeeFirstname AS employee_name,
      e.department,
      s.employeeFirstname AS supervisor_name
  FROM employees e
  LEFT JOIN employees s ON e.supervisor_id = s.employeeid;
  ```
  
  ## Key Points
  
  - **Self-join**: Join the table to itself using different aliases (`e` for employee, `s` for supervisor)
  - **LEFT JOIN**: Use this to include employees who don't have a supervisor (like the CEO) - they'll show `NULL` for supervisor_name
  - **Join condition**: `e.supervisor_id = s.employeeid` links each employee to their supervisor's record
  
  ## Example
  
  | employeeid | employeeFirstname | department | supervisor_id |
  |------------|-------------------|------------|---------------|
  | 1          | Alice             | Engineering| NULL          |
  | 2          | Bob               | Engineering| 1             |
  | 3          | Carol             | Sales      | 1             |
  
  **Result:**
  
  | employee_name | department  | supervisor_name |
  |---------------|-------------|-----------------|
  | Alice         | Engineering | NULL            |
  | Bob           | Engineering | Alice           |
  | Carol         | Sales       | Alice           |
  
  ---
  
  **Follow-up questions** interviewers might ask:
  - What if you only want employees who *have* a supervisor? (Use `INNER JOIN`)
  - How would you find employees with no supervisor? (Add `WHERE s.employeeid IS NULL`)
  - How would you show the full hierarchy? (Recursive CTE)
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## 📸 File History Snapshot (2025-12-06T03:01:10.624Z)
## ◂ USER
  you have excel table, date, call_count, department, category, week. count all calls for operatoins catergory for week 5
## ◆ ASSISTANT
  This is a **filtering and aggregation** question. You need to filter rows by two conditions and sum the call count.
  
  ## Solution
  
  ```sql
  SELECT SUM(call_count) AS total_calls
  FROM calls
  WHERE category = 'operations'
    AND week = 5;
  ```
  
  ## Key Points
  
  - **WHERE**: Filters to only rows matching both conditions
  - **SUM()**: Adds up all call_count values from matching rows
  - **AND**: Both conditions must be true
  
  ---
  
  **Follow-up variations** they might ask:
  - Count calls per department for week 5: `GROUP BY department`
  - Count calls for each week in operations: `GROUP BY week`
  - Show only departments with more than 100 calls: `HAVING SUM(call_count) > 100`
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