Oracle and DateTime math

Please provide the data types for all the columns involved.

Assuming WAL's startyime is a varchar2, I would convert it to a date then back into the individual values and do a simple join to sessions.

Here is the conversion of WAL.  Then just add the join.

with cte as (
select to_date(starttime,'MM/DD/YYYY HH:MI:SS AM') starttime_as_date from wal
)
select to_char(starttime_as_date,'fmMM/"1"/YYYY') startdate, to_char(starttime_as_date,'fmDD'), to_char(starttime_as_date,'HH24MI') starttime
from cte
/

Try this as a complete example:

with cte as (
select to_date(starttime,'MM/DD/YYYY HH:MI:SS AM') starttime_as_date, key from wal
)
select startdate, sessionday, s.starttime, key
from sessions s
	join cte c on s.startdate=to_char(starttime_as_date,'fmMM/"1"/YYYY')
		and s.sessionday=to_char(starttime_as_date,'fmDD')
		and s.starttime= to_char(starttime_as_date,'HH24MI')
/

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I'm writing a query to select some records. I have this data:

Event Table
------------------
Definition
    EVE_RID         NUMBER(10)
    EVE_START_DATE  Date

Data:
    EVE_RID     EVE_START_DATE
    156891      11/1/2016

Agenda Table
------------------
Definition:
    AGD_EVE_RID     NUMBER(10)
    AGD_DAY         NUMBER(2)
    AGD_START_TIME  NUMBER(4)

Data:
AGD_EVE_RID     AGD_DAY     AGD_START_TIME
156891          1           1000     
156891          1           1400     
156891          8           1000     
156891          8           1400     
156891          15          1000     
156891          15          1400     

WAList Table
------------------
Definition:
    WAL_STARTTIME   DATE
    WAL_KEY         VARCHAR2(50)

Data:
WAL_STARTTIME           WAL_KEY                
11/1/2016 10:00:00 AM   6341371019318098180
11/1/2016 2:00:00 PM    7561779448126279684
11/8/2016 10:00:00 AM   6904435321948802820
11/8/2016 2:00:00 PM    7998296559469684996
11/15/2016 10:00:00 AM  4690144247933554180
11/15/2016 2:00:00 PM   7931460546152111876

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What I need is some way to match records from the WAList table from the Agenda table.
How could I write my where clause to match the WALList records to the Event.EVE_START_DATE + Agenda.AGD_DAY records and return the correct Key for the correct day? This would be result:

EVE_START_DATE   AGD_DAY    AGD_START_TIME  WAL_KEY                
11/1/2016       1           1000            6341371019318098180
11/1/2016       1           1400            7561779448126279684
11/1/2016       8           1000            6904435321948802820
11/1/2016       8           1400            7998296559469684996
11/1/2016       15          1000            4690144247933554180
11/1/2016       15          1400            7931460546152111876

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Thanks.