The sub-dominant of Db is Gb.
The subdominant note is D in an A major scale
Yes. Actually it's spelled "subdominant" but that's just getting picky.
The subdominant is the 4th note in a scale, so in A major it's D.
The D note
D (natural)
G
The Keys of B-flat, E-Flat, A-Flat, D-Flat, G-Flat, C-Flat, and F-Flat major all contain the note E-flat. F-flat major is a key which only exists in theory and not in practice, since there is a double flat in that scale (subdominant). The major scale with the most flats is C-flat major - with all seven flats.
The pentatonic scale has 5 notes. It is similar to the omission of subdominant and leading note of major scale. Starting from D, the scale is D E F# A B.
The subdominant note is the fourth scale degree of any key, for example in C major the subdominant note is F since the scale goes C D E F G A B C.
D major(D,F#,A,D) for sub domonant, and E major(E,G#,B,E) for dominant
D.
The subdominant of D major is G major.