ORACLE: 

1、查主键名称： select * from user_constraints where table_name = 'AAA' and constraint_type ='P'; 

查主键对应的列： select * from user_cons_columns where table_name = 'AAA' and constraint_name = 'PK_AAA'; (PK_AAA 是主键名)

2、查索引名称： select * from user_indexes where table_name = 'AAA'; 查索引对应的列： select * from user_ind_columns where table_name = 'AAA' and index_name = 'INDX_BA'; (INDX_BA 是 索引名)

了解几个字典表的用处 如：user_constraints 

添加主键：

alter table TableName

add constraint PK NAMEprimary key("ACCOUNTINGTASKID"...);

删除主键：

alter table EXTRACTED_POSTING(tablle name)

drop constraint EXTRACTED_POSTING_ACCTID_PK;(PK name)