Sv: Oracle SQL engine?

Hey Johnnie,

There are no differences between your 2 'selects'.

The first 'select a.*' means that you want the entire table 'dual a' displayed.

On the other hand is very usefull if you have to related table where you only want to
display some information.

Norris <johnnie_at_cooper.com.hk> skrev i en nyhedsmeddelelse:7o6siq$kto$1_at_imsp009a.netvigator.com...
> Can anybody tell me the differences between the following two SQL?
>
> select a.* , dummy from dual a
> /

sql>select a.start_date,b.emp_name from project a,emp b sql>where a.emp_id=b.emp_id

Could show you all the project startdates that have been initaiated by each employee.

It dosn't have to be 'a,b,c etc' but could also be 'me, loan, others'.

> select * , dummy from dual a
> /
>
> --
> ===================================
> http://www.washington.edu/pine/faq/

If you are running vldb you should be carefull to join tables like this, hence you could
set the proccesor in progress of many hours at work.

Some little advice :

Table a = 10.000 records
Table b = 5.000.000 records
Table c = 10.000.000.000 records

A 'select * from table a,table b, table c' should be interpetreted as a request that is
10.000 multiplied 5.000.000 multiplied 10.000.000.000, which is BIG number. For some reason only Oracle can answer this 'select' is slower than : select * from table c,table b, table a. I think its because of the Oracle/sql compiler.

Do visit http://www.orcmag.com.code.tip06049.html>

with regards Allan Received on Tue Aug 03 1999 - 10:04:22 CDT