Serial types

How Can I restart the values of a serial type field...??

I mean, I have a table with id_user defined as serial type, if a delete the
data from this table and insert new data the field id_user will start the
counter from the last record it had saved...

So... I want the new records insert into the table begins again with 1.

I used alter table <table> alter id_user set default 1;

But, only I could insert one record with number 1.

Thanks for your answers.

Sonny

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para no perderse con mentiras
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