How many times does the word "riu" appears in the biwords pair?
riu refers to word = 'riu'; SUM(w1st where wid is word = 'riu' AND w2nd where wid is word = 'riu')
SELECT COUNT(T1.wid) FROM words AS T1 INNER JOIN biwords AS T2 ON T1.wid = T2.w1st INNER JOIN words AS T3 ON T3.wid = T2.w2nd WHERE T1.word = 'riu'
database name:db_id language_corpus
langs table langs Cols: language id dtype integer, language dtype text, locale dtype text, pages dtype integer, words dtype integer, 
pages table pages Cols: page id dtype integer, language id dtype integer, page dtype integer, revision dtype integer, title dtype text, words dtype integer, 
words table words Cols: word id dtype integer, word dtype text, occurrences dtype integer, 
langs_words table langs_words Cols: language id dtype integer, word id dtype integer, occurrences dtype integer, 
pages_words table pages_words Cols: page id dtype integer, word id dtype integer, occurrences dtype integer, 
biwords table biwords Cols: language id dtype integer, word id of the first word dtype integer, word id of the second word dtype integer, occurrences dtype integer, 
