1. In SQL, we can use count in the query to get the number of a column in the table.
query = "select count(birth_rate) from facts;"
2. Also, we can use AVG, SUM,MIN, MAX to get the different property of a column
query = "select min(population_growth) from facts"
3. WE can also use mutiple aggregation function in a single query, and it will return mutiple tuples in a list
query_mix = "select avg(population),sum(population),max(birth_rate) from facts"
4. We can use DISTINCT function to choose the unique element in a table.
query = "select distinct birth_rate from facts"
5. Distinct can be combined with aggregate function.
query = "select avg(distinct birth_rate) from facts where population > 20000000"
6. Column and column can do arithmetic in the query. For arithmetic operation, float with float get float, float and integer get float, integer and integer get integer.
query = "select population_growth/1000000.0 from facts" # The result is float
