SQL语句解析函数

function SQL语句解析函数($sql)                {
    global $db,$MetaTables;
    //判断自定义表是否存在,如果不存在直接返回

    //判断是否是联合全操作,是否有子查询,是否用left
    //如果有,则表示为手写SQL代码,不是系统生成,则直接返回,不进行过滤
    $sql        = trim($sql);
    $sqllower   = strtolower($sqllower);
    if(substr($sqllower,0,strlen("create table"))=="create table")      {
        return $sql;
    }
    if(substr($sqllower,0,strlen("drop table"))=="drop table")          {
        return $sql;
    }
    if(substr($sqllower,0,strlen("check table"))=="check table")        {
        return $sql;
    }
    if(substr($sqllower,0,strlen("optimize table"))=="optimize table")  {
        return $sql;
    }
    if(substr($sqllower,0,strlen("repair table"))=="repair table")      {
        return $sql;
    }
    if(substr($sqllower,0,strlen("analyze table"))=="analyze table")    {
        return $sql;
    }

    //进行关键字过滤
    $sql = eregi_replace(" From "," from ",$sql);
    $sql = eregi_replace(" FROM "," from ",$sql);

    $sql = eregi_replace(" Where "," where ",$sql);
    $sql = eregi_replace(" WHERE "," where ",$sql);

    $sql = eregi_replace(" Select "," select ",$sql);
    $sql = eregi_replace(" SELECT "," select ",$sql);

    $sql = eregi_replace(" Order By "," order by ",$sql);
    $sql = eregi_replace(" ORDER BY "," order by ",$sql);

    $sql = eregi_replace(" Update "," update ",$sql);
    $sql = eregi_replace(" UPDATE "," update ",$sql);

    $sql = eregi_replace(" Delete "," delete ",$sql);
    $sql = eregi_replace(" DELETE "," delete ",$sql);

    $sql = eregi_replace(" Limit "," limit ",$sql);
    $sql = eregi_replace(" LIMITE "," limit ",$sql);

    $sql = eregi_replace(" Left "," left ",$sql);
    $sql = eregi_replace(" LEFT "," left ",$sql);

    //处理SELECT
    if(substr($sql,0,strlen("select "))=="select ")     {
        $FromArray = explode(" from ",$sql);
        //分析旧的SQL
        if($FromArray[1]!="")                 {
            $FromSelectArray        = explode("select ",$FromArray[0]);
            $SQLArray['SelectText'] = $FromSelectArray[1];
            $FromWhereArray         = explode(" where ",$FromArray[1]);
            $SQLArray['FromText']   = $FromWhereArray[0];
            //如果是两个表,直接返回,不做处理
            $FromTablesArray        = explode(",",$SQLArray['FromText']);
            if($FromTablesArray[1]!='')         {
                print "两个表";
                return $sql;
            }
            //拆分数据库和表
            $FromDBArray            = explode(".",$SQLArray['FromText']);
            if($FromDBArray[1]!="")                   {
                $SQLArray['FromText']   = $FromDBArray[1];
                $SQLArray['DBText']     = $FromDBArray[0];
            }
            $SQLArray['WhereText']  = $FromWhereArray[1];
            $FromOrderByArray       = explode(" order by ",$SQLArray['WhereText']);
            if($FromOrderByArray[1]!="")                  {
                $SQLArray['WhereText']  = $FromOrderByArray[0];
                $SQLArray['OrderByText']= $FromOrderByArray[1];
            }
        }
        //处理新的SQL,之前要进行判断表自定义表是否存在
        $TABLENAME = $SQLArray['FromText'];
        $TABLENAME2 = "view_".$TABLENAME;
        if(in_array($TABLENAME2,$MetaTables))                   {
            //自定义表存在
            $MetaColumnNames    = $db->MetaColumnNames($TABLENAME);
            $MetaColumnNames    = array_keys($MetaColumnNames);
            $原表主键   = $MetaColumnNames[0];
            $MetaColumnNames2   = $db->MetaColumnNames($TABLENAME2);
            $MetaColumnNames2   = array_keys($MetaColumnNames2);
            $新表主键   = $MetaColumnNames2[0];
            array_shift($MetaColumnNames2);
            $自定义表字段列表 = join(',',$MetaColumnNames2);
            $SQLArray['SelectText'] .= ",".$自定义表字段列表;
            $SQLArray['FromText']   .= ",".$TABLENAME2;
            if($SQLArray['WhereText']!="")        {
                $SQLArray['WhereText'] .= " and ".$TABLENAME.".".$原表主键."=".$TABLENAME2.".".$新表主键."";
            }
            else    {
                $SQLArray['WhereText']  = " ".$TABLENAME.".".$原表主键."=".$TABLENAME2.".".$新表主键."";
            }
        }
        else    {
            //不存在,直接返回
            return $sql;
        }
        //形成新的SQL文件
        $NEWTEXTSQL = "select ".$SQLArray['SelectText']." from ".$SQLArray['FromText']."";
        if(TRIM($SQLArray['WhereText'])!="")      {
            $NEWTEXTSQL .=" where ".$SQLArray['WhereText'];
        }
        if(TRIM($SQLArray['OrderByText'])!="")        {
            $NEWTEXTSQL .=" order by ".$SQLArray['WhereText'];
        }
        //形成后返回
        return $NEWTEXTSQL;
        //SELECT  部分结束
    }

    //UPDATE

    //DELETE

    //INSERT INTO



    print_R($NEWTEXTSQL);
    print_R($SQLArray);


}