My Indices doesn't work

Hi *,

I have pgsql7.0.2 on Linux2.2.16 and table with following indices:

CREATE TABLE T1 (NUM INT NOT NULL, NAME VARCHAR(10) NOT NULL, POP
VARCHAR(10) NOT NULL);
CREATE INDEX T1_I_NUM ON T1(NUM);
CREATE INDEX T1_I_NAME ON T1(NAME);
CREATE INDEX T1_I_POP ON T1(POP);

... and some data, but I really don't understant how indices work, look
at that:

template1=# explain select * from t1 where num=2;
NOTICE: QUERY PLAN:
Index Scan using t1_i_num on t1 (cost=0.00..8.14 rows=10 width=28)

what is ok, ***BUT***

template1=# explain select * from t1 where num>2;
NOTICE: QUERY PLAN:
Seq Scan on t1 (cost=0.00..22.50 rows=333 width=28)

WHY SEQ SCAN ?!!?

thank you

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#md