1. SQL 篇

1. 根据一个spbh字段分组, 然后取分组后每个spbh的created最新值

select * from (
   select * from t_user having 1 ORDER BY created desc
   ) a GROUP BY spbh

2. 时间戳格式化

SELECT FROM_UNIXTIME(create_time / 1000, '%Y-%m-%d')                  as createTime

3. 查看当前mysql连接下，每个库的总大小

select TABLE_SCHEMA,
       concat(truncate(sum(data_length) / 1024 / 1024 / 1024, 2), 'GB') as data_size,
       concat(truncate(sum(index_length) / 1024 / 1024, 2), 'MB')       as index_size
from information_schema.tables
group by TABLE_SCHEMA
order by data_length desc;

4.修改 tp 数据库的名称，查看当前数据库下，每个表的总大小

select TABLE_NAME,
       concat(truncate(data_length / 1024 / 1024 / 1024, 2), 'GB')  as data_size,
       concat(truncate(index_length / 1024 / 1024 / 1024, 2), 'GB') as index_size
from information_schema.tables
where TABLE_SCHEMA = 'tp'
group by TABLE_NAME
order by data_length desc;

2. Mybaties篇

1. Mybaties,字符串Foreach循环遍历

<foreach collection="region.split(',')" open="(" separator="," close=")" item="regionParam" index="index">
                #{regionParam}
 </foreach>

2. 大于小于的书写

create_time <![CDATA[ <= ]]> #{endTime}

3. 模糊查询的书写

device_name like concat('%',#{deviceName},'%')