Minor: Update documentation of case expression (#7646)

* docs: update case expression

* Format with prettier

docs/source/user-guide/expressions.md

@@ -139,11 +139,11 @@ Unlike to some databases the math functions in Datafusion works the same way as
 
 ## Conditional Expressions
 
-| Function | Notes                                                                                                                                                                                                    |
-| -------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
-| coalesce | Returns the first of its arguments that is not null. Null is returned only if all arguments are null. It is often used to substitute a default value for null values when data is retrieved for display. |
-| case     | CASE expression. Example: `case(expr).when(expr, expr).when(expr, expr).otherwise(expr).end()`.                                                                                                          |
-| nullif   | Returns a null value if `value1` equals `value2`; otherwise it returns `value1`. This can be used to perform the inverse operation of the `coalesce` expression.                                         |
+| Function | Notes                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
+| -------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| coalesce | Returns the first of its arguments that is not null. Null is returned only if all arguments are null. It is often used to substitute a default value for null values when data is retrieved for display.                                                                                                                                                                                                                                                                                                                                                                                                                    |
+| case     | CASE expression. The expression may chain multiple `when` expressions and end with an `end` or `otherwise` expression. Example:</br> <pre><code>case(col("a") % lit(3))</br>&nbsp;&nbsp;&nbsp;&nbsp;.when(lit(0), lit("A"))</br>&nbsp;&nbsp;&nbsp;&nbsp;.when(lit(1), lit("B"))</br>&nbsp;&nbsp;&nbsp;&nbsp;.when(lit(2), lit("C"))</br>&nbsp;&nbsp;&nbsp;&nbsp;.end()</code></pre>or, end with `otherwise` to match any other conditions: <pre><code>case(col("b").gt(lit(100)))</br>&nbsp;&nbsp;&nbsp;&nbsp;.when(lit(true), lit("value > 100"))</br>&nbsp;&nbsp;&nbsp;&nbsp;.otherwise(lit("value <= 100"))</code></pre> |
+| nullif   | Returns a null value if `value1` equals `value2`; otherwise it returns `value1`. This can be used to perform the inverse operation of the `coalesce` expression.                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
 
 ## String Expressions