Postgresql과 Oracle 차이점

--sysdate
oracle : select sysdate from dual;
postgresql : select now();

--dual table
oracle : select 1,2 from dual;
postgresql : select 1,2;

--sequence
oracle : sequence_name.nextval
postgresql : nextval.sequence_name

--decode
oracle : decode(column1, val1, result1, ......, default)
postgresql : case columns1 when val1 then result1 .... else default END

--nvl
oracle : NVL(hire_date, SYSDATE) - 타입 불일치 시 묵시적 형변환 발생
postgresql : coalesce(hire_date, SYSDATE) - 컬럼타입 불일치 시 오류(상수는 OK)

--from절 subquery
oracle : select * from (select * from table_name);
postgresql : select * from (select * from table_name) as alias_name;

--outer join
oracle : select a.field1, b.field2 from a, b where a.item_id = b.item_id(+);
postgresql : select a.field1, b.field2 from a left outer join b on a.item_id = b.item_id;

--connected by
oracle : connected by
postgresql : with recursive

--CLOB
oracle : CLOB
postgresql : TEXT

-- 수치비교
oracle : 문자-숫자 비교시 묵시적 형변환 발생
postgresql : 문자-숫자 비교시 오류 발생