CREATE TABLE table_51594 ("City" TEXT, "Country" TEXT, "IATA" TEXT, "ICAO" TEXT, "Airport" TEXT)

What is the IATA of Madrid-Barajas Airport?
SELECT "IATA" FROM table_51594 WHERE "Airport" = 'madrid-barajas airport'
SELECT "IATA" FROM "table_51594" WHERE "Airport" = 'madrid-barajas airport'