vyber z dvoch tabuliek

select stlpec1, stlpec2, stlpec3 from tab1 where stlpec3 is not null
union all
select stlpec1, stlpec2, stlpec3 from tab2 where stlpec3 is not null
order by stlpec3 desc

select stlpec1, stlpec2, stlpec3, table_name from tab1, information_schema.tables where stlpec3 is not null  and table_name = 'tab1'
union all
select stlpec1, stlpec2, stlpec3, table_name from tab2, information_schema.tables where stlpec3 is not null and table_name = 'tab2'
order by stlpec3 desc

select stlpec1, stlpec2, stlpec3, 'tab1' as stlpec4 from tab1 where stlpec3 is not null
union all
select stlpec1, stlpec2, stlpec3, 'tab2' as stlpec4 from tab2 where stlpec3 is not null
order by stlpec3 desc