SELECT count(*) FROM Person WHERE age  >  30 AND job  =  'engineer'
How many people whose age is greater 30 and job is engineer?
[Schema (values) (types)]: | network_2 |  Person : name (text) , age (text) , city (number) , gender (text) , job (text) | PersonFriend : name (text) , friend (text) , year (number);