Question-37

In SQL, relations can contain null values, and comparisons with null values are treated as unknown. Suppose all comparisons with a null value are treated as false. Which of the following pairs is not equivalent?

• \(x=5, \text{not}(\text{not}(x=5))\)
• \(x=5, x>4\) and \(x<6\), where \(x\) is an integer
  
• \(x\neq 5, \text{not}(x=5)\)
  
• none of the above

Answer

• \(x=5, \text{not}(\text{not}(x=5))\)
• \(x=5, x>4\) and \(x<6\), where \(x\) is an integer
  
• \(x\neq 5, \text{not}(x=5)\)
  
• none of the above