MySQL字段与表的注释。转帖

Posted 2021-03-03 区块链散户一枚

 

# comment    评论；意见；批评；描述

1,新建表以及添加表和字段的注释.
   create table t_user(
        ID INT(19) primary key auto_increment  comment ‘主键‘,
        NAME VARCHAR(300) comment ‘姓名‘,
        CREATE_TIME date comment ‘创建时间‘
    )comment  = ‘用户信息表‘;

# 字段内在字段最后面添加COMMENT 注释 ,括号外面用COMMENT=‘‘来给表添加注释

2,修改表/字段的注释.
     　　alter table t_user comment  = ‘修改后的表注释信息(用户信息表)‘;
    　　 alter table t_user modify column id int comment ‘主键ID‘;
   --注意：字段名和字段类型照写就行

3,查询数据库所有表的详细信息(包括表的注释).
use information_schema;
select * from TABLES where TABLE_SCHEMA=‘你的表所在的数据库‘;
--查询某一张表的
use information_schema;
select * from TABLES where TABLE_SCHEMA=‘你的表所在的数据库‘ and TABLE_NAME= ‘你的表名‘;

mysql> SELECT * FROM TABLES WHERE table_schema=‘test‘ AND table_name=‘test1‘G
*************************** 1. row ***************************
  TABLE_CATALOG: def
   TABLE_SCHEMA: test
     TABLE_NAME: test1
     TABLE_TYPE: BASE TABLE
         ENGINE: InnoDB
        VERSION: 10
     ROW_FORMAT: Dynamic
     TABLE_ROWS: 0
 AVG_ROW_LENGTH: 0
    DATA_LENGTH: 16384
MAX_DATA_LENGTH: 0
   INDEX_LENGTH: 0
      DATA_FREE: 0
 AUTO_INCREMENT: NULL
    CREATE_TIME: 2020-03-26 22:47:59
    UPDATE_TIME: NULL
     CHECK_TIME: NULL
TABLE_COLLATION: utf8_general_ci
       CHECKSUM: NULL
 CREATE_OPTIONS: 
  TABLE_COMMENT: 我是表解释
1 row in set (0.00 sec)

 

4,查询一张表的详细信息(包括字段注释,字段名称,类型等).
use information_schema;
select * from information_schema.columns where table_schema =‘你的表所在的数据库‘  and table_name = ‘你的表名‘;

mysql> mysql> SELECT * FROM COLUMNS WHERE table_schema=‘test‘ AND table_name=‘test1‘G
*************************** 1. row ***************************
           TABLE_CATALOG: def
            TABLE_SCHEMA: test
              TABLE_NAME: test1
             COLUMN_NAME: tt
        ORDINAL_POSITION: 1
          COLUMN_DEFAULT: NULL
             IS_NULLABLE: YES
               DATA_TYPE: int
CHARACTER_MAXIMUM_LENGTH: NULL
  CHARACTER_OCTET_LENGTH: NULL
       NUMERIC_PRECISION: 10
           NUMERIC_SCALE: 0
      DATETIME_PRECISION: NULL
      CHARACTER_SET_NAME: NULL
          COLLATION_NAME: NULL
             COLUMN_TYPE: int(11)
              COLUMN_KEY: 
                   EXTRA: 
              PRIVILEGES: select,insert,update,references
          COLUMN_COMMENT: 我是解释
   GENERATION_EXPRESSION: 
1 row in set (0.00 sec)

mysql> 

 

注:还有一种方式:

# 查看建表语句，可以看到你的表注释与字段注释

show create table table_name;

mysql> SHOW CREATE TABLE test1G
*************************** 1. row ***************************
       Table: test1
Create Table: CREATE TABLE `test1` (
  `tt` int(11) DEFAULT NULL COMMENT ‘我是解释‘
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT=‘我是表解释‘
1 row in set (0.00 sec)

mysql> 

 

# SHOW 方式可以查看你的字段注释
show full columns from 表名;

mysql> SHOW FULL COLUMNS FROM test1;
+-------+---------+-----------+------+-----+---------+-------+---------------------------------+--------------+
| Field | Type    | Collation | Null | Key | Default | Extra | Privileges                      | Comment      |
+-------+---------+-----------+------+-----+---------+-------+---------------------------------+--------------+
| tt    | int(11) | NULL      | YES  |     | NULL    |       | select,insert,update,references | 我是解释     |
+-------+---------+-----------+------+-----+---------+-------+---------------------------------+--------------+
1 row in set (0.00 sec)

mysql> 

 

所以总结来看，如果想查看表与字段的信息，最好通过建表语句来看。

就是SHOW CREATE TABLE xxx，这个最方便