Merge pull request #287 from NReilingh/patch-2

corrects inaccuracies in truth tables for AND/OR

Author: barbkess

docs/t-sql/language-elements/null-and-unknown-transact-sql.md

@@ -36,23 +36,23 @@ ms.workload: "On Demand"
 
 -   Null values cannot be used as information that is required to distinguish one row in a table from another row in a table, such as primary keys, or for information used to distribute rows, such as distribution keys.  
 
- When null values are present in data, logical and comparison operators can potentially return a third result of UNKNOWN instead of just TRUE or FALSE. This need for three-valued logic is a source of many application errors. These tables outline the effect of introducing null comparisons.  
+ When null values are present in data, logical and comparison operators can potentially return a third result of UNKNOWN instead of just TRUE or FALSE. This need for three-valued logic is a source of many application errors. Logical operators in a boolean expression that includes UNKNOWNs will return UNKNOWN unless the result of the operator does not depend on the UNKNOWN expression. These tables provide examples of this behavior.  
 
- The following table shows the results of applying an AND operator to two Boolean operands where one operand returns NULL.  
+ The following table shows the results of applying an AND operator to two Boolean expressions where one expression returns UNKNOWN.  
 
-|Operand 1|Operand 2|Result|  
+|Expression 1|Expression 2|Result|  
 |---------------|---------------|------------|  
-|TRUE|NULL|FALSE|  
-|NULL|NULL|FALSE|  
-|FALSE|NULL|FALSE|  
+|TRUE|UNKNOWN|UNKNOWN|  
+|UNKNOWN|UNKNOWN|UNKNOWN|  
+|FALSE|UNKNOWN|FALSE|  
 
- The following table shows the results of applying an OR operator to two Boolean operands where one operand returns NULL.  
+ The following table shows the results of applying an OR operator to two Boolean expressions where one expression returns UNKNOWN.  
 
-|Operand 1|Operand 2|Result|  
+|Expression 1|Expression 2|Result|  
 |---------------|---------------|------------|  
-|TRUE|NULL|TRUE|  
-|NULL|NULL|UNKNOWN|  
-|FALSE|NULL|UNKNOWN|  
+|TRUE|UNKNOWN|TRUE|  
+|UNKNOWN|UNKNOWN|UNKNOWN|  
+|FALSE|UNKNOWN|UNKNOWN|  
 
 ## See Also  
  [AND (Transact-SQL)](../../t-sql/language-elements/and-transact-sql.md)