Sales Person - Problem

You're working as a data analyst for a sales management company, and you need to identify which salespersons have never dealt with the RED company. This is important for business strategy - perhaps the RED company is a competitor, or maybe they're planning to reassign territories.

You have access to three related database tables:

  • SalesPerson: Contains salesperson details (ID, name, salary, commission rate, hire date)
  • Company: Contains company information (ID, name, city)
  • Orders: Contains order records linking salespersons to companies

Your task is to find all salespersons who have NEVER had any orders related to the company named "RED". Think of it as finding the "clean" salespersons who haven't been involved with this particular company.

The challenge here is dealing with the absence of data - you need to find people who are NOT in a certain subset of records.

Input & Output

example_1.sql — Basic Case
$ Input: SalesPerson: [{id:1,name:'Amy'}, {id:2,name:'Bob'}] Company: [{id:1,name:'RED'}, {id:2,name:'BLUE'}] Orders: [{sales_id:1,com_id:1}, {sales_id:2,com_id:2}]
› Output: ['Bob']
💡 Note: Amy worked with RED company (com_id=1), but Bob only worked with BLUE company (com_id=2). So Bob never worked with RED.
example_2.sql — No RED Orders
$ Input: SalesPerson: [{id:1,name:'John'}, {id:2,name:'Jane'}] Company: [{id:1,name:'GREEN'}, {id:2,name:'RED'}] Orders: [{sales_id:1,com_id:1}, {sales_id:2,com_id:1}]
› Output: ['John', 'Jane']
💡 Note: Both John and Jane only worked with GREEN company. Neither has any orders with RED company, so both are returned.
example_3.sql — All Have RED Orders
$ Input: SalesPerson: [{id:1,name:'Tom'}, {id:2,name:'Sara'}] Company: [{id:1,name:'RED'}] Orders: [{sales_id:1,com_id:1}, {sales_id:2,com_id:1}]
› Output: []
💡 Note: Both Tom and Sara have orders with RED company, so no salespersons qualify for the result.

Visualization

Tap to expand
All SalespersonsAmy, Bob, CharlieDavid, EveRED CompanyOrders from:Amy, CharlieClean ListNever worked with RED:Bob, David, EveAmyBobCharlieDavidEveFilterResult🔵 Worked with RED🟢 Never worked with RED
Understanding the Visualization
1
Identify the Problem Client
First, we identify 'RED' as our target company in the Company table
2
Find All RED Interactions
Create a list of all salespersons who have had orders with RED company
3
Compare Against Full Team
Use LEFT JOIN to compare this list against all salespersons
4
Extract the Clean List
Filter for salespersons who don't appear in the RED interactions list
Key Takeaway
🎯 Key Insight: Use LEFT JOIN to find the absence of relationships - it's more efficient than checking presence with NOT IN subqueries

Time & Space Complexity

Time Complexity
⏱️
O(n + m + k)

Linear scan of all tables with efficient join operations

n
2n
✓ Linear Growth
Space Complexity
O(k)

Temporary space for join results, where k is number of unique salespersons with RED orders

n
2n
✓ Linear Space

Related Problems

Constraints

  • 1 ≤ Number of salespersons ≤ 105
  • 1 ≤ Number of companies ≤ 104
  • 0 ≤ Number of orders ≤ 106
  • Company names are case-sensitive
  • All sales_id and com_id values are valid foreign keys
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