Cross_Joins

Question

What is CROSS JOIN with an empty table ??

Answer 1

IT WILL MAKE TABLE WITH ALL ATTTRIBUTES OF BOTH TABLES.

AS IF IN FUTURE, WE WANT TO INSERT  WE CAN INSERT IN THAT TABLE.

2ND TABLE IS EMPTY NOW BUT IN FUTURE WE CAN INSERT VALUE IN THAT TABLE ATTRIBUTES ,SO FROM MY POINT OF VIEW IT WILL CREATE TABLEWITH ALL ATTRIBUTES OF BOTH TABLE

Comments

OPTION A IS MUCH MORE COMPATIBLE AS COMPARED TO OTHER OPTIONS.

SO A OPTION WILL BE TRUE THERE @daksirp

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ya, thats fine about compatibility. i just wanted to knoe how it is empty set. anyway thanx :)

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let T1 have m rows, x columns and T2 have n rows, y columns

the no.of rows in the cross product = m*n ------ (1)

the no.of columns in the cross product = x+y ----(2)

 

in empty relation, rows necessarily 0, but columns not necessarily 0

from (1), it should result 0 rows