https://www.postgresql.org/docs/9.5/static/functions-math.html

select random()* 10

제약조건 생성 SQL

snippet.sql

ALTER TABLE distributors
  ADD  CONSTRAINT zipchk CHECK (LENGTH(zipcode) = 6);

수정이 바로 되지 않으므로 drop 후에 add 합니다.

snippet.sql

ALTER TABLE distributors
  DROP CONSTRAINT zipchk
, ADD  CONSTRAINT zipchk CHECK (LENGTH(zipcode) = 6);

생성 SQL

snippet.sql

ALTER TABLE public.event_info_ps
  DROP CONSTRAINT event_info_ps_ck1
  , ADD CONSTRAINT event_info_ps_ck1 CHECK (event_state_type::text = ANY (ARRAY['0001'::CHARACTER VARYING, '0002'::CHARACTER VARYING, '0003'::CHARACTER VARYING]::text[]));

• http://dba.stackexchange.com/questions/122689/modify-table-constraint-in-postgresql

현재 시각을 출력할 때 now() 함수를 사용한다.

https://www.postgresql.org/docs/9.5/static/functions-formatting.html

포맷 변환

snippet.sql

SELECT to_char(now(), 'YYYYMMDDHH24MISS');

SELECT now() + interval '-30 days'

https://www.postgresql.org/docs/9.0/static/functions-datetime.html

위와 같은 에러가 나오면 CREATE EXTENSION dblink; 구문을 실행합니다.

그 후 접속 테스트를 합니다.

snippet.sql

SELECT dblink_connect('host=localhost user=postgresuser password=enjoy dbname=postgres');

각각, host, user, password, dbname 을 정확히 입력합니다.

위의 에러가 발생하면, dblink 사용시에 해당 결과를 받을 수 있도록 타입을 모두 지정해 주어야 합니다.

snippet.sql

SELECT p.* FROM dblink('host=localhost user=postgresuser password=postgrespassword dbname=mydb', 'select code_type from my.common_code') AS p(code_type VARCHAR(10))

• http://www.postgresonline.com/journal/archives/44-Using-DbLink-to-access-other-PostgreSQL-Databases-and-Servers.html

http://www.postgresqltutorial.com/postgresql-foreign-key/

snippet.sql

ALTER TABLE child_table 
  ADD CONSTRAINT constraint_name FOREIGN KEY (c1) REFERENCES parent_table (p1);