CREATE TABLE table_204_798 (id NUMBER, "year" NUMBER, "competition" CLOB, "venue" CLOB, "position" CLOB, "notes" CLOB)

how many world championships did imamura participate in ?
SELECT COUNT(*) FROM table_204_798 WHERE "competition" = 'world championships'
SELECT COUNT(*) FROM "table_204_798" WHERE "competition" = 'world championships'