I tried to solve 1075. ‘Project Employees I’.

# Problem

``````1075. Project Employees I
``````

problem

# Correct Solution

``````select project_id, round(avg(experience_years),2) as average_years
from Project left outer join Employee
on Project.employee_id = Employee.employee_id
group by Project.project_id;
``````

# Memo

## Round

``````ROUND(num [ , n ])
``````
• 1) source
The source argument is a number or a numeric expression that is to be rounded.
• 2) n
The n argument is an integer that determines the number of decimal places after rounding.
The n argument is optional. If you omit the n argument, its default value is 0.

Ref

``````_pg_db=# select round(100.00);
round
-------
100
(1 row)

_pg_db=# select round(10.123456);
round
-------
10
(1 row)

_pg_db=# select round(10.123456, 2);
round
-------
10.12
(1 row)

_pg_db=# select round(10.123456, 4);
round
---------
10.1235
(1 row)
``````

## Agv

Get average

``````AVG(column)
``````

Ref

``````_pg_db=# create table t1(a int);
CREATE TABLE

_pg_db=# insert into t1 values (1);
INSERT 0 1
_pg_db=# insert into t1 values (2);
INSERT 0 1
_pg_db=# insert into t1 values (3);
INSERT 0 1
_pg_db=# select avg(a) from t1;
avg
--------------------
2.0000000000000000
(1 row)
``````