Bueno mi conocimiento se ha ampliado :
una de las formas es esta (seguro que hay mas):
Código PHP:
( CAST(Dia1 AS integer) + CAST(Dia2 AS integer) + CAST(Dia3 AS integer) + CAST(Dia4 AS integer) + CAST(Dia5 AS integer) + CAST(Dia6 AS integer)
+ CAST(Dia7 AS integer) + CAST(Dia8 AS integer) + CAST(Dia9 AS integer) + CAST(Dia10 AS integer) + CAST(Dia11 AS integer) + CAST(Dia12 AS integer)
+ CAST(Dia13 AS integer) + CAST(Dia14 AS integer) + CAST(Dia15 AS integer) + CAST(Dia16 AS integer) + CAST(Dia17 AS integer)
+ CAST(Dia18 AS integer) + CAST(Dia19 AS integer) + CAST(Dia20 AS integer) + CAST(Dia21 AS integer) + CAST(Dia22 AS integer)
+ CAST(Dia23 AS integer) + CAST(Dia24 AS integer) + CAST(Dia25 AS integer) + CAST(Dia26 AS integer) + CAST(Dia27 AS integer)
+ CAST(Dia28 AS integer) + CAST(Dia29 AS integer) + CAST(Dia30 AS integer) + CAST(Dia31 AS integer)) AS DiasTrabajados
parecía más dificil...
