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Five ways to query MySQL field comments!

2022-07-05 01:28:00 【Brother Lei talks about programming】

A lot of scenarios , We need to check MySQL Notes to middle table , Or the notes of all fields under a table , So this article will count and compare several ways of querying comments .

Create test database

Before we start, let's create a database , For the following demonstration .

       
        --  If it exists, delete the database first 
        
drop database if exists test2022;
        
--  Create database 
        
create database test2022;
        
--  Switch database 
        
use test2022;
        
--  Create tables and fields （ And corresponding notes ）
        
CREATE TABLE `student` (
        
  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT ' Student number ',
        
  `sn` varchar(50) DEFAULT NULL COMMENT ' Student number ',
        
  `username` varchar(250) NOT NULL COMMENT ' Student name ',
        
  `mail` varchar(250) DEFAULT NULL COMMENT ' mailbox ',
        
  `class_id` int(11) DEFAULT NULL,
        
  PRIMARY KEY (`id`)
        
) comment=' Student list ' ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4
       
       
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Query all table comments

Use the following SQL You can query the comments of all tables under a database ：

       
        SELECT table_name  Table name , table_comment  Table description 
        
  FROM information_schema.TABLES 
        
  WHERE table_schema=' Database name '
        
  ORDER BY table_name
       
       
        1.
        2.
        3.
        4.

Case study ： Inquire about test2022 All table annotations in the database ：

       
        SELECT table_name  Table name , table_comment  Table description 
        
  FROM information_schema.TABLES 
        
  WHERE table_schema='test2022'
        
  ORDER BY table_name
       
       
        1.
        2.
        3.
        4.

The execution result is shown in the figure below ：

Inquire about MySQL Field comment 5 Methods ！_ Table name

Query all field comments

Field annotation query method 1

The query syntax is as follows ：

       
        show full columns from  Table name ;
       
       
        1.

Case study ： Inquire about student Comment information for all fields in the table ：

       
        show full columns from student;
       
       
        1.

The execution result is shown in the figure below ：

Inquire about MySQL Field comment 5 Methods ！_ Field _02

Field annotation query method 2

The query syntax is as follows ：

       
        select COLUMN_NAME  Field name ,column_comment  Field description ,column_type  Field type ,
        
  column_key  constraint  from information_schema.columns 
        
  where table_schema=' Database name ' and table_name=' Table name ';
       
       
        1.
        2.
        3.

Case study ： Inquire about student Comment information for all fields in the table ：

       
        select COLUMN_NAME  Field name ,column_comment  Field description ,column_type  Field type ,
        
  column_key  constraint  from information_schema.columns 
        
  where table_schema='test2022' and table_name='student';
       
       
        1.
        2.
        3.

The execution result is shown in the figure below ：

Inquire about MySQL Field comment 5 Methods ！_ Table name _03

Field annotation query method 3

Query table DDL（ Data definition language ） You can also see the comment content of the field , Executive SQL The grammar is as follows ：

       
        show create table  Table name ;
       
       
        1.

Case study ： Inquire about student Comment information for all fields in the table ：

       
        show create table student;
       
       
        1.

The execution result is shown in the figure below ：

Inquire about MySQL Field comment 5 Methods ！_ Table name _04

Field annotation query method 4

If you are using Navicat Tools , You can right-click on the table 、 More design , You can view the field comments on the design page , As shown in the figure below ：

Inquire about MySQL Field comment 5 Methods ！_ Field _05

But this kind of operation is a little dangerous , Be careful to shake your hands and correct the structure of the watch .

Field annotation query method 5

stay Navicat View the table in DDL Statement can also see the field comments , Select the table and click the lower right foot “ Show the right window ” Options , Then click DDL You can show , The specific operation steps are shown in the figure below ：

Inquire about MySQL Field comment 5 Methods ！_ database _06

Modify table comments and field comments

Modify table notes

Modify the syntax of table comments ：

       
        alter table  Table name  comment =' Modified table comments ';
       
       
        1.

Case study ： modify student Table comments for ：

       
        alter table student  comment =' Student list  V2';
       
       
        1.

The execution result is shown in the figure below ：

Inquire about MySQL Field comment 5 Methods ！_ database _07

Modify field comments

Modify the syntax of table comments ：

       
        alter table  Table name  modify column  Field name  int comment ' Annotation information ';
       
       
        1.

Case study ： modify student In the table name Notes ：

       
        alter table student modify column username int comment ' The student's name  V2';
       
       
        1.

The execution result is shown in the figure below ：

Inquire about MySQL Field comment 5 Methods ！_ Table name _08

summary

This article introduces how to view table comments SQL, And modify the notes of tables and fields SQL, It also introduces how to view field comments 5 Methods ：3 A command line operation mode to view , Two methods based on Navicat How to operate view , Which is recommended SQL：“show full columns from Table name ” View field comments , This kind of inquiry SQL Simple and don't worry about changing the table structure by mistake .

It's up to you to judge right and wrong , Disdain is to listen to people , Gain or loss is more important than number .
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Inquire about MySQL Field comment 5 Methods ！_ Field _09