Make JSON from SQL query output

I have this database query:

select hostname,size from tableinfo

The output is like this:

hostname                   size
------------------------- -----------
  host1                        28
  host2                        13
  host3                        79
  host4                        28
  host5                        17

Or, I can make it like this:

host1                        28
host2                        13
host3                        79
host4                        28
host5                        17

I want to write a shell script that converts this output to JSON, but I don't really know where to begin or what to do. The JSON must be like this:

{
    "data":[
    {  "{#HOSTNAME}":"host1",  "{#SIZE}":"28"  } ,
	{  "{#HOSTNAME}":"host2",  "{#SIZE}":"13"  } ,
	{  "{#HOSTNAME}":"host3",  "{#SIZE}":"79"  } ,
	{  "{#HOSTNAME}":"host4",  "{#SIZE}":"28"  } ,
	{  "{#HOSTNAME}":"host5",  "{#SIZE}":"17"  }
    ]
}