苞米豆的多資料來源 → dynamic-datasource-spring-boot-starter，挺香的！

CREATE DATABASE datasource_mysql;
USE datasource_mysql;
CREATE TABLE tbl_user (
    id INT UNSIGNED NOT NULL AUTO_INCREMENT,
    user_name VARCHAR(50),
    PRIMARY KEY(id)
);
INSERT INTO tbl_user(user_name) VALUES('張三'),('李四');

CREATE DATABASE datasource_mssql;
USE datasource_mssql;
CREATE TABLE tbl_order(
    id BIGINT PRIMARY KEY IDENTITY(1,1),
    order_no NVARCHAR(50),
    created_at DATETIME NOT NULL DEFAULT(GETDATE()),
    updated_at DATETIME NOT NULL DEFAULT(GETDATE())
);
INSERT INTO tbl_order(order_no) VALUES('123456'),('654321');

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.lee</groupId>
    <artifactId>mybatis-plus-dynamic-datasource</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.10.RELEASE</version>
    </parent>

    <properties>
        <java.version>1.8</java.version>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <mybatis-plus-boot-starter.version>3.1.1</mybatis-plus-boot-starter.version>
        <mssql-jdbc.version>6.2.1.jre8</mssql-jdbc.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>${mybatis-plus-boot-starter.version}</version>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>dynamic-datasource-spring-boot-starter</artifactId>
            <version>${mybatis-plus-boot-starter.version}</version>
        </dependency>
        <!-- MySQL驅動-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>

        <!-- SQL Server 驅動-->
        <dependency>
            <groupId>com.microsoft.sqlserver</groupId>
            <artifactId>mssql-jdbc</artifactId>
            <version>${mssql-jdbc.version}</version>
        </dependency>
    </dependencies>
</project>

server:
  port: 8081
spring:
  application:
    name: dynamic-datasource
  datasource:
    dynamic:
      datasource:
        mssql_db:
          driver-class-name: com.microsoft.sqlserver.jdbc.SQLServerDriver
          url: jdbc:sqlserver://10.5.108.225:1433;DatabaseName=datasource_mssql;IntegratedSecurity=false;ApplicationIntent=ReadOnly;MultiSubnetFailover=True
          username: sa
          password: Root#123456
        mysql_db:
          driver-class-name: com.mysql.cj.jdbc.Driver
          url: jdbc:mysql://10.5.108.225:3306/datasource_mysql?useSSL=false&useUnicode=true&characterEncoding=utf-8&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=Asia/Shanghai
          username: root
          password: 123456
      primary: mssql_db
      strict: false

mybatis-plus:
  mapper-locations: classpath:mappers/*.xml
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl