CREATE TABLE table_203_212 (id NUMBER, "#" NUMBER, "district" CLOB, "land area  ( km2 ) " NUMBER, "population\ ( 2010 census ) " NUMBER, "density  ( persons/km2 ) " NUMBER)

which district has the most density ?
SELECT "district" FROM table_203_212 ORDER BY "density (persons/km2)" DESC LIMIT 1
SELECT "district" FROM "table_203_212" ORDER BY "density (persons/km2)" DESC FETCH FIRST 1 ROWS ONLY