Write SQL query to solve given problem: How many times greater is the appearances of the biword pair "a base" than "a decimal"?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT CAST(occurrences AS REAL) / ( SELECT occurrences FROM biwords WHERE w1st = ( SELECT wid FROM words WHERE word = 'a' ) AND w2nd = ( SELECT wid FROM words WHERE word = 'decimal' ) ) FROM biwords WHERE w1st = ( SELECT wid FROM words WHERE word = 'a' ) AND w2nd = ( SELECT wid FROM words WHERE word = 'base' )