0 votes 0 votes Here why does the 5th query select * from employees natural join works_on where PID = 'X' AND PID='Y'; is not working The queries are The output are Databases sql databases relational-algebra + – kd..... asked Apr 30, 2019 • retagged Jun 18, 2019 by Cristine kd..... 683 views answer comment Share Follow See all 10 Comments See all 10 10 Comments reply Show 7 previous comments srestha commented May 2, 2019 reply Follow Share @ankitgupta.1729 check this point too, and check 2nd table. There 1 is not the key , but 1,X is the key, because 1 is not unique, but 1,X is unique. Another point think about division operation If there all attributes matches, then only returns. otherwise not return So, it is possible to have 2 values for the query , then returns true.(maynot be in same row definitely) right? 0 votes 0 votes ankitgupta.1729 commented May 2, 2019 reply Follow Share not getting mam... question is not related to key.. suppose instead of condition PID='X' and PID ='Y', If condition is PID='X' and NAME='A' then what should be output acc. to u and how it comes? 0 votes 0 votes srestha commented May 2, 2019 reply Follow Share @ankitgupta.1729 I havenot got , what ur query is. Plz. see this example PID=X, say X means employee who wear white shirt. PID=Y, say Y means employee who wear red tie Those who wear both can enter in Company. Can this not a possibility? 0 votes 0 votes Please log in or register to add a comment.