CREATE TABLE table_3952 ("Code" TEXT, "District" TEXT, "Headquarters" TEXT, "Population  ( 2001 Census ) " FLOAT, "Population  ( 2011 Census ) " FLOAT, "Area  ( km\\u00b2 ) " FLOAT, "Density in 2011  ( /km\\u00b2 ) " TEXT)

What's the code of the district in which 312520 people lived in 2011?
SELECT "Code" FROM table_3952 WHERE "Population (2011 Census)" = '312520'
SELECT "Code" FROM "table_3952" WHERE "Population (2011 Census)" = '312520'