'Find the difference in seconds between two dates [duplicate]

I have following query in oracle to get diff in seconds

SELECT TO_DATE('a', 'dd-mm-yyyy hh24:mi:ss') - TO_DATE(Q'b', 'dd-mm-yyyy hh24:mi:ss') 
FROM dual

i'm looking for equivalent query in postgres

Solution 1:^[1]

You can do it like this:

SELECT EXTRACT(EPOCH FROM (timestamp1- timestamp2)) FROM dual

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Solution	Source
Solution 1