NULL is not determinate value and is not counted when the COUNT function is used with the DISTINCT keyword
For instance, if you SELECT DISTINCTÂ MANAGER_ID from EMPLOYEES; you will get 19 rows with NULL among them.
However, if you do SELECT COUNT(DISTINCT MANAGER_ID) from EMPLOYEES; you will get just 18
It is a little tricky, so keep in mind. The guaranteed situation on the exam.
NULL is not determinate value and is not counted when the COUNT function As we can see when you supply NULL explicitly […]
RR, YY and YYYY masks will interpret variable length years, means you can specify both two-digit or four-digit format as shown […]
These two queries will produce identical results: IN =ANY
Using NOT IN is fraught with problems because of the way SQL handles NULLs. As a general rule, do not use NOT IN […]
