Any difference in these queries?

[Chang Gee Guan]

Let say i have a Table (Customer)

And i had written two queries:

i. select cust_id, cust_name, cust_add, cust_age from Customer where cust_id>1000
ii.select c.cust_id, c.cust_name, c.cust_add, c.cust_age from Customer c where cust_id>1000

These two queries will give the same output, but, they have differences in terms of performance.
Which 1 will perform better? Or they are just the same?

[CK]

surely is the (ii) o becoz AOA

[Chang Gee Guan]

surely is the (ii) o becoz AOA

because AOA??? hahahaha....

any more concrete answer why second query will run faster than the first 1?

[CK]

what i ting is because the sql statement had create a alias table name for customer which is "c".
so when select stament "c.cust_id" is execute, it is faster compare to normal select statement "cust_id" which actually equally to "customer.cust_id" where it will search by the long table name "customer".
 

[CK]

(i)SELECT city FROM country WHERE city!= 'Vancouver' AND city!= 'Toronto'; GROUP BY city;
 
(ii)SELECT city FROM country GROUP BY city HAVinG city!= 'Vancouver' AND city!= 'Toronto';

so, any idea which queries is faster,hehe

[mysteriousdrx]

which is faster?mm...i think that depends on your processor speed..haha 
but i think its the first one..

[CK]

(i)SELECT city FROM country WHERE city!= 'Vancouver' AND city!= 'Toronto'; GROUP BY city;
 
(ii)SELECT city FROM country GROUP BY city HAVinG city!= 'Vancouver' AND city!= 'Toronto';

so, any idea which queries is faster,hehe

the ans is avoid a HAVING clause in SELECT statements becoz it only filters selected rows after all the rows have been returned. Use HAVING only when summary operations applied to columns will be restricted by the clause. A WHERE clause may be more efficient.

[Chang Gee Guan]

haha...
thanks for sharing these info.
hope it will help others to optimize their code.