问题

Table ‘zup.Domain_System’ doesn’t exist

### The error occurred while setting parameters
### SQL: SELECT * FROM Domain_System         WHERE domain = ? LIMIT 1
### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'zup.Domain_System' doesn't exist
; bad SQL grammar []; nested exception is com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'zup.Domain_System' doesn't exist] with root cause

解决问题

首先可以肯定我数据库中是存在这个表的，只是全是小写的，而SpringBoot项目中的是开头大写字母的

在mysql 5.7.x版本中默认是大小写区分的。

可以登录mysql之后查看show variables like "%case%";：

lower_case_table_names=0，默认为0，则区分大小写

truedei@truedei:/codeProject$ sudo mysql -h 127.0.0.1 -u root -p
Enter password: 
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.29 MySQL Community Server (GPL)

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MySQL [(none)]> show variables like "%case%";
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| lower_case_file_system | OFF   |
| lower_case_table_names | 0     |
+------------------------+-------+
2 rows in set (0.00 sec)

MySQL [(none)]> 

所以解决方法就是修改mysql中的配置文件，让其忽略大小写：

因为我使用的是docker安装的mysql5.7，并且把配置文件映射到 了：/data/mysql/conf/my.conf

修改配置文件my.conf

truedei@truedei:~$ 
truedei@truedei:~$ sudo vim /data/mysql/conf/my.conf 

添加上：

lower_case_table_names=1

保存

我在这里就需要重启docker，你如果是直接安装的mysql，可以直接重新mysql即可

truedei@truedei:~$ 
truedei@truedei:~$ sudo docker ps -a
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                               NAMES
0a122a08125f        mysql:5.7.29        "docker-entrypoint.s…"   2 hours ago         Up 4 minutes        0.0.0.0:3306->3306/tcp, 33060/tcp   mysql57
truedei@truedei:~$ 
truedei@truedei:~$ 
truedei@truedei:~$ 
truedei@truedei:~$ sudo docker restart mysql57
mysql57
truedei@truedei:~$ 

可以看到变成了1

truedei@truedei:/codeProject$ sudo mysql -h 127.0.0.1 -u root -p
Enter password: 
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.29 MySQL Community Server (GPL)

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MySQL [(none)]> 
MySQL [(none)]> show variables like "%case%";
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| lower_case_file_system | OFF   |
| lower_case_table_names | 1     |
+------------------------+-------+
2 rows in set (0.00 sec)

MySQL [(none)]> 

就可以解决此问题