ThinkPHP5多个数据库查询注意项

1. 数据库切换
   i. 在config.php中添加数据库配置数组

//数据库配置1
'db_config1' => [
// 数据库类型
'type' => 'mysql',
// 服务器地址
'hostname' => '127.0.0.1',
// 数据库名
'database' => 'thinkphp',
// 数据库用户名
'username' => 'root',
// 数据库密码
'password' => '',
// 数据库编码默认采用utf8
'charset' => 'utf8',
// 数据库表前缀
'prefix' => 'think_',
],
//数据库配置2
'db_config2' => 'mysql://root:1234@localhost:3306/thinkphp#utf8';

将查询语句改成(这里要用‘->’连接table()方法；之前是‘::’)

Db::connect('db_config1')->table('test1')->field('*')->select();
Db::connect('db_config2')->table('test1')->field('*')->select();

1. 将特定的SQL语句修改为TP5的链式操作
   原SQL语句如下：

SELECT parent.name, COUNT(product.name)
FROM nested_category AS node,
nested_category AS parent,
product
WHERE node.lft BETWEEN parent.lft AND parent.rgt
AND node.category_id = product.category_id
GROUP BY parent.name
ORDER BY node.lft

使用默认的数据库配置时

$res = Db::table('nested_category node,nested_category parent,product')
            ->field('parent.name,count(product.name)')
            ->where('node.category_id','exp', '= product.category_id')
            ->where('node.lft','exp', 'between parent.lft and parent.rgt')
            ->group('parent.name')
            ->order('node.lft')
            ->select();

使用第二个数据库配置时(table()前用‘->’连接；且多个数据库名用‘[]’包围，转为数组)

$testConnect = Db::connect('test_conf');
$res = $testConnect->table(['nested_category node,nested_category parent,product'])
            ->field('parent.name,count(product.name)')
            ->where('node.category_id','exp', '= product.category_id')
            ->where('node.lft','exp', 'between parent.lft and parent.rgt')
            ->group('parent.name')
            ->order('node.lft')
            ->select();