比如我执行了这样一句SQL：
return $this->Model_Field->where('fieldid='.I('post.setting'))->save();
这时，tp报错了：
:(

SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ')' at line 1
错误位置
FILE: F:\wwwroot\crycn\ThinkPHP\Library\Think\Db\Driver.class.php 　LINE: 217

TRACE
#0 F:\wwwroot\crycn\ThinkPHP\Library\Think\Db\Driver.class.php(217): PDOStatement->execute()
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我想获取他组装的SQL语句是什么。请问怎么获取？谢谢