php中的SQL问题无法按预期工作

Hi i have two sql statements the first one is

$sql = "SELECT TOP 2 
    ReaderData.ReaderIndex, 
    ReaderData.CardID,
    ReaderData.ReaderDate, 
    ReaderData.ReaderTime, 
    ReaderData.controllerID, 
    Left([dtReading],10) AS [date], 
    ReaderData.dtReading 
    FROM ReaderData 
    WHERE ReaderData.controllerID=$this->Id 
    ORDER BY ReaderData.ReaderIndex desc;";

and the second one which is

$sql = "SELECT 
    [SHOP FLOOR PRODUCTION PLAN].[MACHINE], 
    [SHOP FLOOR PRODUCTION PLAN].[cycletime]
    WHERE [SHOP FLOOR PRODUCTION PLAN].[MACHINE]=$this->name
    FROM [SHOP FLOOR PRODUCTION PLAN]";

the first one works as expected however the second one does not work with the WHERE in there if i remove it then it spits out one of the enterys in the table and i am not sure why Any help would be appreciated

1. Since I am assuming [SHOP FLOOR PRODUCTION PLAN].[MACHINE] is a string, try putting quotes around the dynamic $this->name part of the query. e.g.

   WHERE [SHOP FLOOR PRODUCTION PLAN].[MACHINE]='$this->name'

2. Also, the WHERE clause must appear after the FROM clause:

   SELECT [SHOP FLOOR PRODUCTION PLAN].[MACHINE], [SHOP FLOOR PRODUCTION PLAN].[cycletime] FROM [SHOP FLOOR PRODUCTION PLAN] WHERE [SHOP FLOOR PRODUCTION PLAN].[MACHINE]='$this->name'