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PG Basics - logical structure management (1)

2022-06-29 13:35:00 【51CTO】

database

Create database

       
       CREATE DATABASE name
       
       [ 
       
       [ WITH 
       
       ] 
       
       [ OWNER 
       
       [
       
       =
       
       ] user_name 
       
       ]   Used to specify which user the new database belongs to , If it is not specified, the user who is currently executing the command 
       
       [ TEMPLATE 
       
       [
       
       =
       
       ] template 
       
       ]     Specify template library 
       
       [ ENCODING 
       
       [
       
       =
       
       ] encoding 
       
       ]     Specify character encoding 
       
       [ LC_COLLATE 
       
       [
       
       =
       
       ] lc_collate 
       
       ]
       
       [ LC_CTYPE 
       
       [
       
       =
       
       ] lc_ctype 
       
       ]
       
       [ TABLESPACE 
       
       [
       
       =
       
       ] tablespace_name 
       
       ]  Specify the associated tablespace 
       
       [ ALLOW_CONNECTIONS 
       
       [
       
       =
       
       ] allowconn 
       
       ]
       
       [ CONNECTION 
       
       LIMIT 
       
       [
       
       =
       
       ] connlimit 
       
       ]  Specify acceptable concurrent connections , Default  
       
       -
       
       1  Don't limit 
       
       [ IS_TEMPLATE 
       
       [
       
       =
       
       ] istemplate 
       
       ] 
       
       ]
      
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modify the database

       
       alter database osdbadb connection 
       
       limit 
       
       10
       
       ;
       
       alter database osdbadb rename to tesetdb01
       
       ;
       
       alter database tesetdb01 owner to cjr
       
       ;
       
       alter database testdb01 
       
       set tablespace new_tablespace
       
       ;
       
       alter database tesedb01 
       
       set enable_indexscan TO off
       
       ;
       
       alter database tesetdb01 reset all
       
       ;
       
       alter database tesetdb reset enable_indexscan
       
       ;
      
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Delete database

      
      
       
       drop database tesetdb01
       
       ;
      
      
      
      
       
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Pattern

Different schemas can have tables with the same name , Functions and other objects do not conflict , As long as you have authority , Objects of various patterns can call each other . stay PG in , You cannot access objects in different databases at the same time , Objects that can access multiple schemas in this database at the same time .

       
       create schema osdba
       
       ;   Create mode 
       
       drop schema osdba
       
       ;     Delete the pattern 
       
       alter schema osdba rename to osdba1
       
       ;   Rename mode 
       
       alter schema osdba1 owner to cjr
       
       ;      Modify the user of the schema 
      
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To create or access objects in a schema , Need to write a modified name , Schema name + Table name

schema_name.table_name

Users cannot access objects in the schema that do not belong to them , To access such an object , The owner of the schema must give them uasge jurisdiction . By default, everyone is public Both modes have create and USAGE jurisdiction , That is to say, all users who can connect to the specified database are allowed to create objects here . You can reclaim this permission

revoke create on schema public from PUBLIC ;

the second PUBLIC All users .

surface

Single primary key table

       
       create 
       
       table test001
       
       (id 
       
       int primary key
       
       ,note 
       
       varchar
       
       (
       
       20
       
       )
       
       )
       
       ;
      
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Compound primary key table

You need to use the syntax of a constraint clause

       
       create 
       
       table test002
       
       (id1 
       
       int
       
       ,id2 
       
       int
       
       , note 
       
       varchar
       
       (
       
       20
       
       )
       
       ,
       
                     CONSTRAINT pk_test002 primary key 
       
       (id1
       
       ,id2
       
       )
       
       )
       
       ;
      
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Unique constraint

       
       create 
       
       table test003
       
       (id1 
       
       int
       
       ,id2 
       
       int
       
       ,id3 
       
       int
       
       ,note 
       
       varchar
       
       (
       
       20
       
       )
       
       ,
       
                     CONSTRAINT pk_test0003 primary key
       
       (id1
       
       ,id2
       
       )
       
       ,
       
                     CONSTRAINT uk_test03_id2 UNIQUE
       
       (id3
       
       )
       
       )
       
       ;
      
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Form creation

create table baby (like test003); But there is no copy constraint ,

Need to add INCLUDE keyword

create table baby1 (like test003 including all);

create table baby2 as select * from test003 with no data;

A temporary table

Session level temporary table , Another transaction level temporary table .

Session level temporary table

       
       create TEMPORARY 
       
       table tmp_t1
       
       (id 
       
       int primary key
       
       ,note 
       
       text
       
       )
       
       ;
      
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Transaction level temporary tables

Session level temporary table , Another transaction level temporary table .

create TEMPORARY table tmp_t1(id int primary key,note text); Session temporary table

create TEMPORARY table tmp_t2(id int primary key,note text) on commit delete rows; Transaction commit data disappears

create TEMPORARY table tmp_t2(id int primary key,note text) on commit PRESERVE ROWS; The data is stored throughout the session

create TEMPORARY table tmp_t2(id int primary key,note text) on commit drop; The transaction commit table disappears

UNLOGGED surface

Don't record wal journal , Abnormal downtime recovery is not possible , Normal shutdown does not affect

create unlogged table unlogged1（id int primary key,t text);

The default value is DEFAULT

upadte student set age=DEFAULT where no=2;

The default value is an expression , It will be calculated when inserting the default value , Instead of creating tables

Modify the default alter table student alter column age set default 15;

Delete default alter table student alter column age drop default;

constraint

Check constraint

       
       create 
       
       table persons
       
       (name 
       
       varchar
       
       (
       
       40
       
       )
       
       ,
       
age 
       
       int check 
       
       (age 
       
       >=
       
       0 
       
       and age
       
       <=
       
       150
       
       )
       
       ,
       
sex 
       
       boolean 
       
       )
       
       ;
      
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Reference constraint name

       
       create 
       
       table persons
       
       (name 
       
       varchar
       
       (
       
       40
       
       )
       
       ,
       
 age 
       
       int CONSTRAINT check_age check 
       
       (age 
       
       >=
       
       0 
       
       and age
       
       <=
       
       150
       
       )
       
       ,
       
 sex 
       
       boolean
       
       )
       
       ;
      
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Writing of constraints

       
       create 
       
       table books
       
       (
       
  book_no 
       
       integer
       
       ,
       
  name 
       
       text
       
       ,
       
  price 
       
       numeric check 
       
       (price 
       
       >
       
       0
       
       )
       
       ,
       
  discounted_price 
       
       numeric check 
       
       (discounted_price 
       
       >
       
       0
       
       )
       
       ,
       
 check
       
       (price
       
       >discounted_price
       
       )
       
       )
       
       ;
      
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The third constraint is not attached to a field , Instead, it appears as a separate line in a comma separated list .

Or so

       
       create 
       
       table books
       
       (
       
book_no 
       
       integer
       
       ,
       
name 
       
       text
       
       ,
       
price 
       
       numeric ,
       
discounted_price 
       
       numeric ,
       
check 
       
       (price 
       
       >
       
       0 
       
       and discounted_price 
       
       >
       
       0 
       
       and price
       
       >discounted_price
       
       )
       
       )
       
       ;
      
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Unique constraint

       
       create 
       
       table books
       
       (
       
book_no 
       
       integer uniqe
       
       ,
       
name 
       
       text
       
       ,
       
price 
       
       numeric
       
       )
       
       ;
       
       create 
       
       table books
       
       (
       
book_no 
       
       integer
       
       ,
       
name 
       
       text
       
       ,
       
price 
       
       numeric
       
UNIQUE
       
       (book_no
       
       )
       
       )
       
       ;
      
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Non empty constraint

not null Decorate the field

Foreign key constraints

       
       create 
       
       table class
       
       (
       
    class_no 
       
       int primary key
       
       ,
       
    class_name 
       
       varchar
       
       (
       
       40
       
       )
       
       )
       
       ;
       
       create 
       
       table student
       
       (
       
    student_no 
       
       int primary key
       
       ,
       
    student_name 
       
       varchar
       
       (
       
       40
       
       )
       
       ,
       
    age 
       
       int
       
       ,
       
    class_no 
       
       int references class
       
       (class_no
       
       )
       
       )
       
       ;
      
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Add constraints

       
       alter tablestudent add check 
       
       (age
       
       <
       
       16
       
       )
       
       ;
      
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Delete constraints

       
       alter 
       
       table student 
       
       drop constraint constraint_name
       
       ;
      
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Delete a non empty constraint. A non empty constraint has no name , You can delete

alter table student alter column student_name drop not null;

Primary key constraint

Primary keys can be created later

alter table books add constraint pk_book_book_no primary key(book_no);

Table related operations

Add fields alter table class add column class_teacher varchar(40);

Delete field alter tableclass drop column class_teacher;

Rename field alter table books rename column book_no to book_id;

rename table alter table books rename to book;

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当前位置：网站首页>PG Basics - logical structure management (1)

PG Basics - logical structure management (1)

database

Create database

modify the database

Delete database

Pattern

surface

Single primary key table

Compound primary key table

Unique constraint

Form creation

A temporary table

Session level temporary table

Transaction level temporary tables

UNLOGGED surface

The default value is DEFAULT

constraint

Check constraint

Unique constraint

Non empty constraint

Foreign key constraints

Add constraints

Delete constraints

Primary key constraint

Table related operations

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