desc dba_objects;
select * from dba_objects where rownum = 6;
select owner, object_id from dba_objects;
select * from dba_objects where object_name = ‘CON$’；
select count(*) from hr.employees;
select count(1) from hr.employees;/rowid进行运算
select distinct(job_id) from hr.employees;
select * from hr.job_history;
select * from departments;
select * from
declare
begin
exception
end;
create or replace
-------------------------------------
null
Null
NULL
‘‘
-------------------------------------
create table nt (id char(10));
alter table nt add columns (sq number);
drop table nt;
insert into nt values (1, ‘null‘);
insert into nt values(2, ‘Null‘)
insert into nt values(3, ‘NULL‘)
insert into nt values(4, ‘ ‘)
insert into nt values(5, null)
insert into nt values(6, Null)
insert into nt values(7, NULL)
select count(1) from nt;
create table nt(sq number, cont varchar(10));
select distinct(cont) from nt;
select last_name, job_id, salary, commission_pct, ‘AAAA‘, ‘BBBB‘ FROM hr.employees;
---------------------------------------------------------------
select table_name from dba_indexes where ;
---------------------------------------------------------------
select ‘‘||index_name||‘‘ from where ;
---------------------------------------------------------------
select department_name || q‘# Manager‘s : #‘ || manager_id from hr.departments;
--------------------------------------------------------------
select distinct department_id from employees;
--------------------------------------------------------------
1、oracle表名都是大写的
2、
------------------------------------------------------------
with tmp as (
select upper(last_name) a, job_id b from employees),;
select a, b from tmp where last_name = ‘Whale‘;
------------------------------------------------------------
show parameter date;
select sysdate from dual;
alter session set nls_data_format = ‘yyyy-mm-dd hh24:mi:ss‘;
------------------------------------------------------------
select sysdate from dual;
select to_char(sysdate, yy-DD-mm);
select to_char(sysdate, ‘yy-dd-mm‘) from dual;
-----------------------------------------------------------
DECLARE
id number;
id:=10;
begin
EXECUTE immediate select * from hr.employees where employee_id = $id;
end;
/
-----------------------------------
原文：https://www.cnblogs.com/niaocaizhou/p/10848237.html