What is the position when the Crewe Alexandra career is 1988 1990, with 31 goals?
CREATE TABLE table_8870 (
    "Name" text,
    "Nationality" text,
    "Position" text,
    "Crewe Alexandra career" text,
    "Appearances" real,
    "Goals" real
)
SELECT "Position" FROM table_8870 WHERE "Crewe Alexandra career" = '1988–1990' AND "Goals" = '31'
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: What is the position when the Crewe Alexandra career is 1988 1990, with 31 goals? ### Input: CREATE TABLE table_8870 (
    "Name" text,
    "Nationality" text,
    "Position" text,
    "Crewe Alexandra career" text,
    "Appearances" real,
    "Goals" real
) ### Response: SELECT "Position" FROM table_8870 WHERE "Crewe Alexandra career" = '1988–1990' AND "Goals" = '31'