Oracle Scenarios Interview Question:

Explain the Dual table. Is any data internally storing in dual table. Lot of users are accessing select sysdate from dual and they getting some millisecond differences. If we execute SELECT SYSDATE FROM EMP; what error will we get and Why?

Submitted by: Administrator

The built-in function SYSDATE returns a DATE value containing the current date and time on your system. DUAL is built-in relation in Oracle which serves as a dummy relation to put in the FROM clause when nothing else is appropriate. For example, try "select 1+2 from dual;".So "select sysdate from EMP" won't generate the desired result.

Select sysdate from emp will not return any error.. It will return sysdate in all the rows. i.e if emp has 100 rows sysdate will be returned 100 times
Submitted by: Administrator