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### 1 文件准备
因为操作MySQL数据库，因此，这里只需要将liquibase安装目录中的example文件中的sql文件夹拷贝出来即可，如：D:\ProgrameFile\liquibase-4.9.1\examples\sql

### 2 修改文件名
sql文件夹中只保留changelog.sql文件和liquibase.properties文件，其中changelog.sql由example-changelog.sql重命名而来

### 3 数据库准备
首先在要操作的MySQL数据库中创建demo数据库

### 4 编辑配置liquibase.properties文件

```bash
# Enter the path for your changelog file.
changeLogFile=changelog.sql

#### Enter the Target database 'url' information  ####
liquibase.command.url=jdbc:mysql://xx.xx.xx.xx:3306/demo

# Enter the username for your Target database.
liquibase.command.username: root

# Enter the password for your Target database.
liquibase.command.password: xxxxxxxxx
```

### 5 编辑changelog.sql文件
如下，创建两个表person和company，然后向person表增加一列country

```bash
--liquibase formatted sql

--changeset redrose2100:1
--comment: create table person
create table person (
    id int primary key auto_increment not null,
    name varchar(50) not null,
    address1 varchar(50),
    address2 varchar(50),
    city varchar(30)
)
--rollback DROP TABLE person;

--changeset redrose2100:2
--comment: create table company
create table company (
    id int primary key auto_increment not null,
    name varchar(50) not null,
    address1 varchar(50),
    address2 varchar(50),
    city varchar(30)
)
--rollback DROP TABLE company;

--changeset redrose2100:3
--comment: add column country to table person
alter table person add column country varchar(2)
--rollback ALTER TABLE person DROP COLUMN country;

```

### 6 打开cmd并进入到sql文件夹下
执行如下命令

```bash
liquibase update
```

执行结果如下：

```bash
D:\src\sql>liquibase update
####################################################
##   _     _             _ _                      ##
##  | |   (_)           (_) |                     ##
##  | |    _  __ _ _   _ _| |__   __ _ ___  ___   ##
##  | |   | |/ _` | | | | | '_ \ / _` / __|/ _ \  ##
##  | |___| | (_| | |_| | | |_) | (_| \__ \  __/  ##
##  \_____/_|\__, |\__,_|_|_.__/ \__,_|___/\___|  ##
##              | |                               ##
##              |_|                               ##
##                                                ##
##  Get documentation at docs.liquibase.com       ##
##  Get certified courses at learn.liquibase.com  ##
##  Free schema change activity reports at        ##
##      https://hub.liquibase.com                 ##
##                                                ##
####################################################
Starting Liquibase at 09:59:17 (version 4.9.1 #1978 built at 2022-03-28 19:39+0000)
Liquibase Version: 4.9.1
Liquibase Community 4.9.1 by Liquibase
Do you want to see this operation's report in Liquibase Hub, which improves team collaboration?
If so, enter your email. If not, enter [N] to no longer be prompted, or [S] to skip for now, but ask again next time [S]:
N
No operations will be reported. Simply add a liquibase.hub.apiKey setting to generate free deployment reports. Learn more at https://hub.liquibase.com
* Updated properties file liquibase.properties to set liquibase.hub.mode=off
Running Changeset: changelog.sql::1::redrose2100
Running Changeset: changelog.sql::2::redrose2100
Running Changeset: changelog.sql::3::redrose2100
Liquibase command 'update' was executed successfully.

D:\src\sql>
```

### 7 进入数据库查看
如下，可以查看到对应的数据库已经创建成功，person表中也已经存在country列
```bash
mysql> use demo;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

### 8 通过命令行方式
这里可以不使用liquibase.properties文件，可以通过使用命令行参数来指定配置，如下：

```bash
liquibase update --changelog-file=changelog.sql --url=jdbc:mysql://xx.xx.xx.xx:3306/demo --username=root --password=xxxxxxxx
```

如此时将changelog.sql文件增加以下修改内容，即向person表增加age一列
```bash
--changeset redrose2100:4
--comment: add column age to table person
alter table person add column age int(3)
--rollback ALTER TABLE person DROP COLUMN age;
```

执行回显如下：
```bash
D:\src\sql>liquibase update --changelog-file=changelog.sql --url=jdbc:mysql://xx.xx.xx.xx:3306/demo --username=root --password=xxxxxxxx
####################################################
##   _     _             _ _                      ##
##  | |   (_)           (_) |                     ##
##  | |    _  __ _ _   _ _| |__   __ _ ___  ___   ##
##  | |   | |/ _` | | | | | '_ \ / _` / __|/ _ \  ##
##  | |___| | (_| | |_| | | |_) | (_| \__ \  __/  ##
##  \_____/_|\__, |\__,_|_|_.__/ \__,_|___/\___|  ##
##              | |                               ##
##              |_|                               ##
##                                                ##
##  Get documentation at docs.liquibase.com       ##
##  Get certified courses at learn.liquibase.com  ##
##  Free schema change activity reports at        ##
##      https://hub.liquibase.com                 ##
##                                                ##
####################################################
Starting Liquibase at 10:10:48 (version 4.9.1 #1978 built at 2022-03-28 19:39+0000)
Liquibase Version: 4.9.1
Liquibase Community 4.9.1 by Liquibase
Do you want to see this operation's report in Liquibase Hub, which improves team collaboration?
If so, enter your email. If not, enter [N] to no longer be prompted, or [S] to skip for now, but ask again next time [S]:
N
No operations will be reported. Simply add a liquibase.hub.apiKey setting to generate free deployment reports. Learn more at https://hub.liquibase.com
* Updated properties file liquibase.properties to set liquibase.hub.mode=off
Running Changeset: changelog.sql::4::redrose2100
Liquibase command 'update' was executed successfully.

D:\src\sql>
```

mysql>
```

### 可能遇到的问题
* 出现如下错误，因为没安装数据库驱动
如下表示liquibase缺少mysql驱动
```bash
Unexpected error running Liquibase: java.lang.RuntimeException: Cannot find database driver: com.mysql.jdbc.Driver
```

解决办法：
下载 mysql-connector-java-5.1.36.jar 包，具体版本根据数据库版本选择，然后放入liquibase的安装目录，这里如：D:\ProgrameFile\liquibase-4.9.1\lib

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