a Newbie needs help

If you find someone has already reply to this message please feel
free to post I really need all of your opinions thanks.

I find the help in the IBO insufficient, please bear with me. Help me
truly understand the following TIB_query properties.

key links: ins't this is use for identifying the primary key or
unique key for the table? Why is it I see it using it in other
purposes like in TIB_lookupcombo? And I have seen an example like
this table1.column1 = table2.colum1, table1.column2 =
table2.column2 ... Iam confious...

if i have a join sql like this "select m.name, d.description,
d2.description from employee m inner join employeetype d on m.type =
d.type inner join department d2 on m.department = d2.department". how
do i fill up the keylink?

before using IB Objects ... I don't see this kind of sql
statement ... "select name,(select description from employeetype d
where m.type = d.type) from employee m". But now I see this kind of
sql statement appear in several examples with IB Objects. Is that
kind of sql statement the same from this kind ... "select m.name,
d.description from employee m inner join employeetype d on m.type =
d.type? If not how do they differ?

join links: it says that it is use when we have implicit join
statement ... what if I have this kind of sql statement ... "select *
from table1 inner join table2 on table1.column1 = table2.column2". Do
I have to use the join links?

what is "FOR UDPATE" sql statement that I usually see at the end of
some TIB_query.sql properties?


Thanks in advance for those who reply this post. I really appreciate
it your making my learning fast.