1 votes 1 votes Is statement 1 true for all safe expressions ? Databases databases relational-algebra relational-calculus + – Harsh181996 asked Jan 24, 2017 Harsh181996 845 views answer comment Share Follow See all 5 Comments See all 5 5 Comments reply Show 2 previous comments Rahul Jain25 commented Jan 24, 2017 reply Follow Share I think relation algebra has safe expressions always. Unsafe are possible only in calculus not algebra.cannot say anything about 3) anyway what is given answrr?? 0 votes 0 votes Harsh181996 commented Jan 25, 2017 reply Follow Share The answer given is D , but @Uddipto statement 1 doesnt explicitly say only relational algebra , it's just a if _ then statement which is true. the explanation given is (as expected) that statement 1 is not always true. Thats why my question can all safe expressions be represented using relational algebra ? 0 votes 0 votes utk0203 commented Oct 16, 2017 reply Follow Share then it might be relational calculus. S 1 not true. 0 votes 0 votes Please log in or register to add a comment.
1 votes 1 votes Answer is D. 1. Relational Calculus has safe expression. 2. Relational Algebra does not generate Unsafe expression. This is true. 3. This is true. 4. All expressions in relation calculus are not safe. Arnab Bhadra answered Feb 6, 2017 Arnab Bhadra comment Share Follow See all 0 reply Please log in or register to add a comment.