Comment on table object_name is ‘comment text’;

create table student(id int,name varchar(250),score decimal(4,1));

comment on table student is 'student information comment';

--指定模式创建表

create schema STU;

create table STU.test(id int,name varchar(30),score decimal(4,1));

comment on table STU.test is 'STU.test information test';

select * from pg_description where objoid ='STU.test'::regclass;

Comment on view object_name is ‘comment text’;

create view student_view as select * from student;

comment on view student_view is 'student_view information comment';

select * from pg_description where objoid=' student_view '::regclass;

--创建视图，然后删除，添加注释

create view student_view2 as select * from student;

comment on view student_view2 is 'student_view2 comment';

drop table student;

comment on view student_view2 is 'student_view2 new comment';

select * from pg_description where objoid=' student_view2'::regclass;

--指定模式创建视图

create view STU.test_view as select * from STU.test;

comment on view STU.test_view is 'STU.test_view comment';

select * from pg_description where objoid='STU.test_view'::regclass;

Comment on column my_table.my_column is ‘comment text’;

create table student(id int,name varchar(250),score decimal(4,1));

comment on column student.name is 'This is student name';

\d+ student

--修改列注释

comment on column student.name is 'new student name comment';

\d+ student

--删除列注释

comment on column student.name is null;

\d+ student

--指定模式为表上的列增加注释

comment on column STU.test_view.name is 'STU.test_view.name column comment';

\d+ STU.test_view

Comment on operator operator_name(left_type,right_type);

comment on operator + (int,int) is 'sum of a+b';

select oid from pg_operator where oprname='+' and oprleft ='int'::regtype and oprright='int'::regtype;

comment on operator * (int,int) is 'multiply of a and b';

select oid from pg_operator where oprname='*' and oprleft ='int'::regtype and oprright='int'::regtype;

Comment on materialized view object_name is ‘comment text’;

create materialized view student_mv as select * from student;

comment on materialized view student_mv is 'this is student_mv comment';

select * from pg_description where objoid='student_mv'::regclass;

Comment on index object_name is ‘comment text’;

create index index_student_id on student(id);

comment on index index_student_id is 'student id index comment';

select * from pg_description where objoid='index_student_id'::regclass;

--删除索引注释

comment on index index_student_id is null;

select * from pg_description where objoid='index_student_id'::regclass;

Comment on table view_name is ‘comment text’;

create table student1(id int,name varchar(30),score decimal(4,1));

create view stu_view as select * from student1;

comment on table stu_view is ' stu_view comment';

\dv+ stu_view

--失效的视图添加注释

create table student2(id int,name varchar(30));

create view stu_view2 as select * from student2;

drop table student2;

comment on table stu_view2 is 'this is comment stu_view2';

\dv+ stu_view2

--给不存在的视图名添加注释

comment on table view1 is 'this is view1 comment';

--指定模式创建视图，并添加注释

create schema ST;

create table ST.test1(id int,name varchar(30),score decimal(4,1));

create view ST.test1_view as select * from ST.test1;

comment on view ST.test1_view is 'ST.test1_view comment information';

\dv+ ST.test1_view