Código SQL [-]select cast(cast(extract(month from fecha) AS CHAR(2))||'/'||'01'||'/'||CAST(extract(year from fecha)) AS CHAR(4)) as date) as fechainicio from tabla
select cast(cast(extract(month from fecha) AS CHAR(2))||'/'||'01'||'/'||CAST(extract(year from fecha)) AS CHAR(4)) as date) as fechainicio from tabla