How to select by value from jsonb field?

Question

PostgreSQL

There is a field in the table with the jsonb type, in it, respectively, the structure {key1:value, key2:value, etc.}
How to write the following queries?
Select table columns and values ​​for field with key1
Select table columns where value key2 = given

Answer 1

select field1,
       jsonb_field -> 'key' as jsonb_value
from mytable
where jsonb_field @> '{"key":"value"}'

Answer 2

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