Group by into single json colum

Question

Using SQL I'd like to convert a table that looks like this

id	col11	col2
1	a	b
1	c	d
2	e	f
2	g	h

Into something that looks like this:

id	combined
1	[{col1: a, col2:b}, {col1: c, col2:d}]
1	[{col1: e, col2:f}, {col1: g, col2:h}]