mysql - Join Only Rows that Match A Certain Condition SQLAlchemy -

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i have 2 tables: a , b

b has foreign key a , b has timestamp field.

a has timestamp field. interested in difference between timestamp fields rows in a , corresponding row in b earliest time stamp. how compute value every row in a?

for example:

a row in a might have 5 rows in b (5/1/2015, 2/3/2014, 2/3/2013). interested in time difference row timestamp of 2/3/2013.

we can join each entry , build table not seem correct approach.

edit: sorry, should have been more specific. using sqlalchemy orm.

add

where b.timestamp = (select min(timestamp) b. x x.id = b.id)

this give min timestamp record.


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