mariadb：SQL日常使用总结

1.关联删除

DELETE T_Base_Resource_Action FROM T_Base_Resource_Action  INNER JOIN T_Base_Resource ON T_Base_Resource_Action.permission = T_Base_Resource.permission
WHERE T_Base_Resource.resID=’course’ AND T_Base_Resource_Action.roleID=’service’ and T_Base_Resource_Action.rootOrgID=’3’;

如果用别名的话就会报错：1109 Unknown table 'T_Base_Resource_Action' in MULTI DELETE

2.查询分区

USE information_schema;

SELECT PARTITION_NAME,TABLE_ROWS
FROM INFORMATION_SCHEMA.PARTITIONS
WHERE TABLE_NAME = 't_gps';

SELECT table_name,table_rows FROM TABLES
WHERE TABLE_SCHEMA = 't_gps'
ORDER BY table_rows DESC;

3.取最新的记录

select *,max(gpsDate) maxDate from t_gps
where gpsDate>='2018-08-29 00:00:00' and gpsDate<='2018-08-29 23:59:59'
group by carCard

备注：记得标准的SQL，非group字段不能放到select中