how many different poll companies are represented ?
CREATE TABLE table_204_639 (
    id number,
    "poll company" text,
    "source" text,
    "publication date" text,
    "psuv" number,
    "opposition" number,
    "undecided" number
)
SELECT COUNT(DISTINCT "poll company") FROM table_204_639
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: how many different poll companies are represented ? ### Input: CREATE TABLE table_204_639 (
    id number,
    "poll company" text,
    "source" text,
    "publication date" text,
    "psuv" number,
    "opposition" number,
    "undecided" number
) ### Response: SELECT COUNT(DISTINCT "poll company") FROM table_204_639