Merging columns from different tables into one table

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1

I have 4 tables that is recording a value (pressure) every 30 seconds (t_stamp). I would like to join the pressures from each table into one single one. I have tried using the union statement, but it seems to join everything into one single column, instead of multiple ones. I am new when it comes to MySQL and would appreciate some help. Thanks!

SS5
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2

Try joining them on the t_stamp instead of union.

3

This is how I had it, can you walk me through what you would do?

4

I usually don't join on a t_stamp. Also, I don't know how much time difference you have in the time values of each table. Either use date_format to trim off the milliseconds or use an interval like below.

select 
    t1.value, t2.value, t3.value, t4.value, t1.t_stamp
from table1 t1
    join table2 t2 on t2.t_stamp between t1.t_stamp - INTERVAL 1 SECOND and t1.t_stamp + INTERVAL 1 SECOND
    join table3 t3 on t3.t_stamp between t1.t_stamp - INTERVAL 1 SECOND and t1.t_stamp + INTERVAL 1 SECOND
    join table4 t4 on t4.t_stamp between t1.t_stamp - INTERVAL 1 SECOND and t1.t_stamp + INTERVAL 1 SECOND

where 
    date(t1.t_stamp) = curdate()
5

Yes, I'd only join on the t_stamp if they follow the same pattern in each table. Otherwise it's... ugly ?