add install & sql

INSTALL

+DROP USER apisub;
+CREATE USER apisub WITH ENCRYPTED PASSWORD 'password';
+DROP DATABASE apisub;
+CREATE DATABASE apisub;
+GRANT ALL PRIVILEGES ON DATABASE apisub TO apisub;

sql/apisub.plantuml

+/** CTRL+ALT+P to view **/
+
+@startuml
+hide circle
+
+class Student {
+  utclogin : text {key}
+  mail : mail {key}
+  surname : text
+  firstname : text
+}
+
+class Api {
+  code : integer {key}
+  name : text
+  year : year
+  semester : H|E
+}
+note right of Api : (name,year,semester) key
+
+Student "0..n" - "0..n" Api
+(Student, Api) . Subscribe
+
+class Subscribe {
+  subdate : date
+}
+
+@enduml

sql/apisub.sql

+DROP TABLE IF EXISTS subscribe CASCADE;
+DROP TABLE IF EXISTS api;
+
+CREATE TABLE api (
+  code INTEGER PRIMARY KEY,
+  name TEXT NOT NULL,
+  year INTEGER NOT NULL,
+  semester CHAR(1) NOT NULL,
+  CHECK (code>0),
+  CHECK (year>2018 AND year<2100),
+  CHECK (semester IN ('H','E')),
+  UNIQUE (name,year,semester)
+);
+
+CREATE TABLE subscribe (
+  utclogin TEXT NOT NULL,
+  api INTEGER REFERENCES api(code),
+  subdate DATE NOT NULL,
+  PRIMARY KEY (utclogin,api)
+);
+
+/** Test dataset **/
+INSERT INTO api VALUES (
+  1,'Poésie et ingénierie',2019,'H'
+);
+INSERT INTO api VALUES (
+  2,'Cloud big data blockchain IA',2019,'H'
+);
+INSERT INTO subscribe VALUES (
+  'crozatst',1,TO_DATE('20181018','YYYYMMDD')
+);
+
+CREATE VIEW vSubscrition AS
+SELECT ap.code, ap.name, ap.year, ap.semester, su.subdate, su.utclogin FROM
+subscribe su JOIN api ap ON ap.code=su.api
+ORDER BY ap.year, ap.semester, su.utclogin, ap.code;