Explicit JOINs vs Implicit joins?

Question

My Database Professor told us to use:

SELECT A.a1, B.b1 FROM A, B WHERE A.a2 = B.b2;

Rather than:

SELECT A.a1, B.b1 FROM A          


        

Answer 1

An average sql query you will encounter in real business has 7-8 joins with 12-16 join conditions. One every 10 or 20 queries may involve nested joins or other more advanced cases. Explicit join syntax is simply far easier to maintain, debug and develop. And those factors are critical for business software - the faster and safer the better. Implicit join are somewhat easier to code if you create statements dynamically through application code. Perhaps there are other uses that i am unaware.