find()返回一个一维数组，select()返回一个二维数组，所以在取值时有所不同，一维数组取值用$data["n"]，二维数组取值用$data[0]["n"]
* * * * *
namespace think\db;
select()方法代码如下：
~~~
/**
* 生成查询SQL
* @access public
* @param array $options 表达式
* @return string
*/
public function select($options = [])
{
$sql = str_replace(
['%TABLE%', '%DISTINCT%', '%FIELD%', '%JOIN%', '%WHERE%', '%GROUP%', '%HAVING%', '%ORDER%', '%LIMIT%', '%UNION%', '%LOCK%', '%COMMENT%', '%FORCE%'],
[
$this->parseTable($options['table'], $options),
$this->parseDistinct($options['distinct']),
$this->parseField($options['field'], $options),
$this->parseJoin($options['join'], $options),
$this->parseWhere($options['where'], $options),
$this->parseGroup($options['group']),
$this->parseHaving($options['having']),
$this->parseOrder($options['order'], $options),
$this->parseLimit($options['limit']),
$this->parseUnion($options['union']),
$this->parseLock($options['lock']),
$this->parseComment($options['comment']),
$this->parseForce($options['force']),
], $this->selectSql);
return $sql;
}
~~~
