Relational algebra - what is the proper way to represent a 'having' clause? -


yes, homework question names have been changed protect innocent. meaning, not asking homework question itself, rather small part of can understand whole.

let's have sql query this:

--the query list car prices occur more once.

select car_price cars group car_price having count (car_price) > 1; 

the general form of in relational algebra y (gl, al) r y greek symbol, gl list of attributes group, al list of aggregations

so relational algebra like:

 y (count(car_price)) cars 

so, how "having" clause written in statement? there shorthand? if not, need select relation? maybe?

select (count(car_price) > 1) [y (count(car_price)) cars] 

i have searched internet on hours , have found no examples of converting having relational algebra. help!

select count(*) (select * cars price > 1) cars;

also known relational closure.


Comments

Popular posts from this blog

unicode - Are email addresses allowed to contain non-alphanumeric characters? -

C#: Application without a window or taskbar item (background app) that can still use Console.WriteLine() -

c++ - Convert big endian to little endian when reading from a binary file -