常用oracle

查看表结构
desc sechma.table

查看表的约束条件

select * from user_constraints where table_name='table_name'

查看主键
select column_name from user_cons_columns wherE CONSTRAINT_NAME in (select CONSTRAINT_NAME from user_constraints where table_name =upper('&tab') and CONSTRAINT_TYPE='P');

constraint_type： p-->主键
                  r-->外键

select a.constraint_name, a.table_name, b.constraint_name
from user_constraints a, user_constraints b
where a.constraint_type = 'R'
and b.constraint_type = 'P'
and a.r_constraint_name = b.constraint_name


插入日期
insert into table values(to_date('年年年年-月月-日日','yyyy-mm-dd'));

查询日期，自定义格式
select to_char(日期字段,'格式化')  from table;