1. select round(123.456)
-> ;
+----------------+
| round(123.456) |
+----------------+
| 123 |
+----------------+
2. 去掉空格
select * from TripTable where driverId=trim("1 ");
3.
select * from TripTable where substr(status,1,2)="等待" ;
+--------+----------+-------------+---------------+----------------+-------------+--------------+-----------+---------------------+
| tripId | driverId | passengerId | startLatitude | startLongitude | endLatitude | endLongitude | status | createAt |
+--------+----------+-------------+---------------+----------------+-------------+--------------+-----------+---------------------+
| 2 | 1 | 1 | 25.4 | 21.2 | 50.1 | 21.2 | 等待单 | 2022-07-25 19:17:55 |
4 字段小写的输出
select lower(driverId) as DriverId from EvaluateTable;
+----------+
| DriverId |
+----------+
| 1 |
| 2 |
| 3 |
| 5 |
| 6 |
| 7 |
| 8 |
| 9 |
| 10 |
+----------+
5. null的坑：
select ename,isNull(sal,0) from emp ;
select ename,isNull(sal,100) from emp;
6. int
varchar
char
date
double
7 日期的类型：
select ename,hiredate from emp where hireDate=str_to_date("1981-12-17","%m-%d-%y")
日期字符串和mysql中默认的字符串不同
直接 insert "1981-12-17" 就是一个varchar
insert into t_student(id,name,brith) values()