(update Set) Blocked field = 1 when there is no sells to one client.

[raosistemas]

have a table client.
---------------------
code Int
blocked tinyint
name varchar

have a table sells.
---------------------
data date
client Int
total float

I want update blocked field with 1 when there is no sells for the client.

[Rabbit]

You should not store the blocked field as that breaks the rules of normalization. Instead you should calculate it as needed.

[Anas Mosaad]

Adding to Rabbit's statement, you have computed fields saved in the database if you want save some processing but you don't care about the size of your data. In some cases, you need to de-normalize for the sake of performance.
If you know that already and still want to keep the field in the DB, you may create a before insert trigger that does this for you.