この席はどなたかいらっしゃいますか。

this (something or someone close to the speaker (including the speaker), or ideas expressed by the speaker)

seat; location (of a gathering, etc.); place; position; post

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

who?

indicates a question (sometimes rhetorical); or; whether or not; some- (e.g. something, someone); indicates doubt, uncertainty, etc.; emphatic prefix; suffix forming adjectives or adverbs; in that way

to come; to go; to be (somewhere); is (doing); are (doing)