Codeigniter重置填充表问题的自动增量

Question

我很困惑。我试图在sql和IT WORKS中执行重置ai代码。

//---------
class iData
{
    virtual const iData&    operator=(const cDataChar&  data) = 0;
    virtual const iData&    operator=(const cDataString& data) = 0;
}
//----------------------------
class cDataChar : public iData
{
    char _data;

    virtual const iData&    operator=(const cDataChar&  data) 
                            { [...implementation...] }
    virtual const iData&    operator=(const cDataString& data)
                            { [...implementation...] }
}
//----------------------------
class cDataString : public iData
{
    string _data;

    virtual const iData&    operator=(const cDataChar&  data) 
                            { [...implementation...] }
    virtual const iData&    operator=(const cDataString& data)
                            { [...implementation...] }
}
//=============================
void
cWorld::main(shared<iData> data1, shared<iData> data2)
{
    if (data2->instanceOf(cDataChar))   
    {
        auto dataChar = static_pointer_cast<cDataChar>(data2);
        (*data1) = (*data2);
    }
    else if (data2->instanceOf(cDataString))    
    {
        auto dataString = static_pointer_cast<cDataString>(data2);
        (*data1) = (*data2);
    }

    // here if i do only (*data1) = (*data2);
    // it doesnt find the right iData::operator= 
    // and goes into the default one.
}

但是当我在CI中这样做时：

SET @num := 0; UPDATE rancangan_bulanan SET id = @num := (@num+1);

它给了我一个错误。

// Location: rb_model.php
function reset_ai() {
    $sql = "SET  @num := 0; UPDATE rancangan_bulanan SET id = @num := (@num+1);";
    $this->db->query($sql);
}

有任何建议吗？