>I created a index on cep (cep_cidade, cep_endereco). Now the result is

faster.

>Is it right to use this way? Can I find problems in the future creating

indexes?

Sounds like a fair index to have, although the query you originally showed
us will not be able to benefit from the second half of the index. If there
are lots of records having the same combination of these two fields, you
may want to include the primary key as the third field in the index as well
(many duplicates slow down updates). The only problem you're likely to
discover, is that IB occationally choose a bad plan and that you'll have to
change your SQL a bit to reduce the number of indexes being used. Say,

SELECT *
FROM table
WHERE A STARTING WITH 'J'
AND B STARTING WITH 'JA'

could be slow if both A and B had an index. In such a case it can be wise
to change so that no index is used for the least restricting criteria, e.g.

SELECT *
FROM table
WHERE (A STARTING WITH 'J' OR 3=2)
AND B STARTING WITH 'JA'

3=2 is of course never true, but because of the OR, Interbase cannot use an
index for A and the query may be able to execute faster. But all this is
just minor thinkering with your SQL which you will discover as you learn.
Get hold of the IB_SQL utility (freeware) from www.ibobjects.com and try
your statements for yourself. You can learn a lot from preparing the SQL
and watching the generated plan.

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