CREATE TABLE table_204_639 (id NUMBER, "poll company" CLOB, "source" CLOB, "publication date" CLOB, "psuv" NUMBER, "opposition" NUMBER, "undecided" NUMBER)

how many total opposition votes were cast after august 2010 ?
SELECT SUM("opposition") FROM table_204_639 WHERE "publication date" > (SELECT "publication date" FROM table_204_639 WHERE "publication date" = 'august 2010')
SELECT SUM("opposition") FROM "table_204_639" WHERE "publication date" > (SELECT "publication date" FROM "table_204_639" WHERE "publication date" = 'august 2010')