Add RIGHT() and LEFT() SQL string functions

[mathiasrw]

Add RIGHT() and LEFT() string functions from SQL

Spawned from #588

[mmaraz]

+1

[garynewelluk]

Presumably these functions only work on varchars and it throws an error if the length supplied is greater than the length of the returned value....

ie

create table myTable (id int, name varchar(10))

insert into myTable (id, name) values (1,'test')

select left(name,3) from myTable  returns 'tes'
select right(name,3) from myTable returns 'est'
select left(name,5) throws error
select right(name,5) throws error
select left(name,0) throws error
select right(name,0) throws error

[rrameshkumar76]

@mathiasrw Is the issue here missing left and right or the error given below ?

it('A) left right', function() {
		var data = [{prop: 'abcdef'}];
		var res = alasql('SELECT left(prop,1) FROM ? ', [data]);
		console.log(res);

	});

This throws error

SELECT left(prop,1) FROM ? 
-------^
Expecting 'LITERAL', 'BRALITERAL', 'EOF'

If this issue is still valid let me know , I can take a look

[mathiasrw]

Yep. Still relevant.

[rrameshkumar76]

@mathiasrw I guess the tricky part is left and right are keywords else where in left/right joins.

if i add a function with slightly diff name like leftstring/rightString they just work versus left/right.

I will see what can be done about this

[mathiasrw]

Yes.

You will need to add the keywords specificly as part of acceptable function names, this way it becomes valid to have those tokens as function names instead of just strings (right now the token LEFT will only be acceptable in relation to join)