How many times on page number 16 does the second word in the pair of words 1 and 109 appear?
How many times appear refer to occurrences; page number 16 refers to pid = 16; Pair is a relationship of two words: w1st and w2nd, where w1st is word id of the first word and w2nd is a word id of the second word; w1st = 1; w2nd = 109;
SELECT SUM(T1.occurrences) FROM pages_words AS T1 INNER JOIN biwords AS T2 ON T2.w2nd = T1.wid WHERE T2.w2nd = 109 AND T2.w1st = 1 AND T1.pid = 16