SQL-grouped in half-month

Full code:

SELECT Sitenumber [Site],convert (VARCHAR (7), day,120) + '-' +case when "day" between 1 and "first half month ' else ' next half month ' end [Half Moon], SUM (Rainval) [half-month rainfall]from R agroup by CONVERT (VARCHAR (7), day,120) + '-' +case "when Day" between 1 and "last Half moon ' Else ' The second half of the month ' End,sitenumber order by Sitenumber, CONVERT (VARCHAR (7), day,120) + '-' +case "when Day" between 1 and then ' upper Half Moon ' El Se ' lower half moon ' end

SQL-grouped in half-month