JOIN (SELECT … ) ue ON 1=1?

Question

I am reading an SQL query in Redshift and can\'t understand the last part:

...
LEFT JOIN (SELECT MIN(modified) AS first_modified FROM user) ue
ON 1=1
         


        

Answer 1

I believe its used to emulate cartesian join.

From your query, the least modified value (It will be just 1 element) will be assigned to all the records of the left table.

PS : Left join is not much useful here. Might as well just use inner join