Convert timestamp column values to epoch in PostgreSQL select query

Question

I need to convert timestamp values to epoch in a SELECT query. Please find the below sample table and expected result.

Sample table:

select          


        

Answer 1

Use the extract() function:

select id, extract(epoch from time) as time, 
       data1, data2,data3
from log;

Apparently your column is not a timestamp column but a varchar, so you first need to cast that to a real timestamp before you can use extract()

select id, 
       extract(epoch from time::timestamp) as time, 
       data1, data2,data3
from log;

This will only work if all values in that column have the correct ISO format for a timestamp.

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This teaches you, that you should

never store date, timestamp or time values in a varchar column!