SELECT STATEMENT QUERY POSTGRES

Question

Help!

I have 2 tables called log shelve and shelve .

Table old shelve has columns old shelve and new shelve :

      A    |    B
      A    |    C
      B    |    C

Table shelve has columns shelve id and shelve description :

      A    | ONE RIGHT 
      B    | ONE LEFT 
      C    | TWO LEFT

I want to get data from those 2 tables, for example:

old shelve	shelve description	new shelve	shelve description
A	ONE RIGHT	B	ONE LEFT
A	ONE RIGHT	C	TWO LEFT
B	ONE LEFT	C	TWO LEFT

Help me thanks

Answer 1

You can join on shelve with different shelve_description.

SELECT 
ls.old_shelve
,os.shelve_desc
,ls.new_shelve
,ns.shelve_desc
FROM log_shelve ls
LEFT JOIN shelve os ON ls.old_shelve = os.shelve_id
LEFT JOIN shelve ns ON ls.new_shelve = ns.shelve_id