Db类注释完善

library/think/Db.php

@@ -11,8 +11,21 @@
 
 namespace think;
 
+use think\db\Query;
+
 /**
- * ThinkPHP 数据库中间层实现类
+ * Class Db
+ * @package think
+ * @method Query table(string $table) static 指定数据表（含前缀）
+ * @method Query name(string $name) static 指定数据表（不含前缀）
+ * @method Query name(string $name) static 指定数据表（不含前缀）
+ * @method Query where($field, $op = null, $condition = null) static 查询条件
+ * @method Query join($join, $condition = null, $type = 'INNER') static JOIN查询
+ * @method Query union($union, $all = false) static UNION查询
+ * @method Query limit($offset, $length = null) static 查询LIMIT
+ * @method Query order($field, $order = null) static 查询ORDER
+ * @method mixed query($sql, $bind = [], $fetch = false, $master = false, $class = false) static SQL查询
+ * @method integer execute($sql, $bind = [], $fetch = false, $getLastInsID = false, $sequence = null) static SQL执行
  */
 class Db
 {