mysql adds comments to data tables and fields

Mysql specific steps to create a table with explanations and add comments to tables and fields:

1. Create a table with explanations

CREATE TABLE test_table( 
　　t_id INT(11) PRIMARY KEY AUTO_INCREMENT COMMENT '设置主键自增',
　　t_name VARCHAR(64) COMMENT '列注释'
) COMMENT='表注释';

2 , Modify table comments

ALTER TABLE test_table COMMENT '修改表注释';

3. View table comments (free learning video tutorial sharing: mysql video tutorial)

SELECT TABLE_COMMENT FROM information_schema.TABLES WHERE TABLE_SCHEMA = 'test' AND TABLE_NAME = 'test_table'

4. Add column comments

alter table test_table add t_age int(11) comment '年龄'

5. Modify the column name with comments

ALTER TABLE test_table CHANGE t_age t_sex VARCHAR(4) COMMENT '性别'

6. Modify the column comments

ALTER TABLE test_table MODIFY COLUMN t_sex VARCHAR(30) NOT NULL COMMENT '男女'

Note: When modifying, you must write the complete definition of the field, such as field type, Properties etc. Never overwrite other attributes defined in this field just to modify a comment.

7. Delete columns

alter table test_table drop column t_sex

8. Query table field information

SHOW FULL COLUMNS FROM test_table

9. Delete tables

-- 单删
　　drop table 表  
-- 批删
　　drop table 表1,表2，表3

10. Modify certain items in batches The field value

UPDATE test_table SET t_name = REPLACE(t_name, 'test', 't')

is as shown in the figure:

Example: Before running

##After running:

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