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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
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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
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The execution result is shown in the figure below :
Query all field comments
Field annotation query method 1
The query syntax is as follows :
show full columns from Table name ;
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Case study : Inquire about student Comment information for all fields in the table :
show full columns from student;
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The execution result is shown in the figure below :
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 ';
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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';
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The execution result is shown in the figure below :
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 ;
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Case study : Inquire about student Comment information for all fields in the table :
show create table student;
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The execution result is shown in the figure below :
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 :
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 :
Modify table comments and field comments
Modify table notes
Modify the syntax of table comments :
alter table Table name comment =' Modified table comments ';
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Case study : modify student Table comments for :
alter table student comment =' Student list V2';
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The execution result is shown in the figure below :
Modify field comments
Modify the syntax of table comments :
alter table Table name modify column Field name int comment ' Annotation information ';
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Case study : modify student In the table name Notes :
alter table student modify column username int comment ' The student's name V2';
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The execution result is shown in the figure below :
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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