aggregation and updated readme

AnuragAnalog · AnuragAnalog · commit 28c049649ee5 · 2019-11-30T04:13:27.000+05:30
diff --git a/README.md b/README.md
@@ -212,4 +212,41 @@ select e.fname, p.pname from employees as e left outer join project as p on e.ei
 #### Right outer join
 ```sql
 select e.fname, p.pname from employees as e right outer join project as p on e.eid = p.eid;
-```
+```
+
+## Aggregation
+
+#### Sum function
+```sql
+select sum(population) from city group by population;
+```
+
+#### Average function
+```sql
+select avg(population) from city group by population;
+```
+
+#### Count function
+```sql
+select count(name) from city group by name;
+```
+
+#### Maximum function
+```sql
+select max(population) from city group by population;
+```
+
+#### Minimum function
+```sql
+select min(population) from city group by population;
+```
+
+#### Standard deviation function
+```sql
+select stddev(population) from city group by population;
+```
+
+#### Group concat function
+```sql
+select group_concat(population) from city group by population;
+```
diff --git a/aggregation.sql b/aggregation.sql
@@ -0,0 +1,44 @@
+
+-- creating basic stuff to work on them
+create database cheatsheet;
+use cheatsheet;
+
+create table city 
+(
+    id int primary key,
+    name varchar(17),
+    countrycode varchar(3),
+    district varchar(20),
+    population int
+);
+
+insert into city values (6, "Rotterdam", "NLD", "Zuid-Holland", 593321);
+insert into city values (3878, "Scottsdale", "USA", "Arizona", 202705);
+insert into city values (3965, "Corona", "USA", "California", 124966);
+insert into city values (3973, "Concord", "USA", "California", 121780);
+insert into city values (3977, "Cedar Rapids", "USA", "Iowa", 120758);
+insert into city values (3982, "Coral Springs", "USA", "Florida", 117549);
+insert into city values (4054, "Fairfield", "USA", "California", 92256);
+insert into city values (4058, "Boulder", "USA", "Colorado", 91238);
+insert into city values (4061, "Fall River", "USA", "Massachusetts", 90555);
+
+-- sum function
+select sum(population) from city group by population;
+
+-- average function
+select avg(population) from city group by population;
+
+-- count function
+select count(name) from city group by name;
+
+-- maximum function
+select max(population) from city group by population;
+
+-- minimum function
+select min(population) from city group by population;
+
+-- standard deviation function
+select stddev(population) from city group by population;
+
+-- group concat function
+select group_concat(population) from city group by population;
