CREATE TABLE groups( 
 gid INT PRIMARY KEY AUTO_INCREMENT COMMENT '设置主键自增',
 gname VARCHAR(200) COMMENT '列注释'
 ) COMMENT='表注释';

alter table test_data modify column test_desc int comment 'xxxx';

ALTER TABLE test_data COMMENT='存放测试用例相关数据'; 

SHOW CREATE TABLE test_data;
#查看表的注释
SELECT table_name,table_comment FROM information_schema.tables WHERE table_schema = 'test' AND table_name ='test_data';

SHOW FULL COLUMNS FROM test_data;
SELECT column_name, column_comment FROM information_schema.columns WHERE table_schema ='test' AND table_name = 'test_data';