Left and Right join

[sandesh-kulkarni]

Is there a way to create left (outer or inner) join and right (outer or inner) join statements?

[twheys]

Yes, when chaining the join function, there is a kwarg called how which takes a pypika.JoinType value

[dabaus]

OMG why not just make an innerJoin function and leftJoin function?
Then you have covered 95% of all usecases for joins.

[twheys]

Because we have real use cases for right and outer joins as well. A single function with a join type argument resulted in less code which was easier to maintain.

[dabaus]

But it creates more complicated code for people using the framework.
I mean, the purpose of this framework was to make it easier for people to write queries instead of using strings. But in this case, this framework results in more complicated code than SQL, so it defeats it's own purpose.

[airtonzanon]

It would be nice to have the functions innerJoin and leftJoin (maybe also for rightJoin).
What do you think to create these functions using the join that PyPika already have?
It would be a small improvement and, maybe will leave the code clearer.

[dabaus]

@airtonzanon Yes it would be nice to have a "syntax sugar" for the most common join types.
I spent some time googling the docs, and then eventually i found out how to make a left join from searching the code on github. It could be easier.

[twheys]

Query
  .from_(table)
  .join(table2, JoinType.left)
  .on(...)

vs .

Query
  .from_(table)
  .left_join(table2)
  .on(...)

I don't really see how the code is any more complicated from API perspective, but definitely not opposed to having some extra join functions that call join passing in the JoinType enum. Feel free to raise a PR, i'll have a look right away.

[twheys]

@dabaus I will look at improving the docs so ensure that the join types are clearly covered.

[airtonzanon]

Nice thing @twheys .

@dabaus Do you want to implement it? I can help if you want, or create the PR. It's your call.

Also, I think, with this PR, we could improve the Documentation of this place. If we try to improve the docs bit a bit, we'll have everything updated.

[twheys]

#348
While writing the docs, I figured it wouldn't take more thn a couple of minutes to add these functions. Mind taking a look at seeing if it meets your expectations?