[Help]How to translate from Algebra->SQL and viceverse?

Hi,

   My professor have teached us how to translate from Logic Language(LL) to SQL, and LL to Algebra, and then in exam appeared question about tranlate Algebra code->SQL code and SQL->Algebra, so I assumed that the only way was through the LL, becasue the direct tranlate from Algebra->SQL is  almost impossible for me, especially with subqueries of more than 4 levels, im talking about kind of monster like this: select(select(select ... where (blablabla) or exists (select ...))); So my first question is: Is there a book i could learn more about this issue from?
One more quesion from the last exam was: "to list all the clients who suffered more than one accidents in Algebra."

table Client(client_id, insurance#,...) <-strong entity (primary key:client_id;foreign key:insurance#)

table Accidents(insurance#, date, time) <-weak entity

to do this one, i used "having count(*)>1" for table Accidents, but the problem is they didnt ask for SQL, so my question is: What is the equivalent algebra codes for "groups ... having ..." ?

Any suggestion will be highly appreciated

best regards Received on Mon Nov 06 2000 - 23:55:05 CET