SQL
`IN` Operator
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The `IN` operator checks containment of the left expression inside the result defined by the subquery or the set of expressions on the right hand side (RHS). The `IN` operator returns true if the expression is present in the RHS, false if the expression is not in the RHS and the RHS has no `NULL` values, or `NULL` if the expression is not in the RHS and the RHS has `NULL` values.  
We can use the `IN` operator in a similar manner as we used the `EXISTS` operator:  
```sql
SELECT 'Math' IN (SELECT course FROM grades) AS math_grades_present;
```  
| math_grades_present |
|--------------------:|
| true                |