MySQL的：和/或质疑

Question

是这样的：

update batchinfo set instrument='Instrument 17' where 
datapath like '%10497%' or 
datapath like '%10506%' or 
datapath like '%10516%' or 
datapath like '%11081%' 
and instrument='Instrument 1' 

与此相同：

update batchinfo set instrument='Instrument 17' where 
datapath like '%10497%' and instrument='Instrument 1' or 
datapath like '%10506%' and instrument='Instrument 1' or 
datapath like '%10516%' and instrument='Instrument 1' or 
datapath like '%11081%' and instrument='Instrument 1' 

Answer 1

否 - 也是唯一有资格datapath like '%11081%'。

不要冒险 - 使用括号。他们更便宜。

Answer 2

没有，但是这两者是等价的：

update batchinfo 
set instrument='Instrument 17' 
where 
    (datapath like '%10497%' or 
    datapath like '%10506%' or 
    datapath like '%10516%' or 
    datapath like '%11081%') 
    and instrument='Instrument 1' 

和

update batchinfo 
set instrument='Instrument 17' 
where 
    (datapath like '%10497%' and instrument='Instrument 1') or 
    (datapath like '%10506%' and instrument='Instrument 1') or 
    (datapath like '%10516%' and instrument='Instrument 1') or 
    (datapath like '%11081%' and instrument='Instrument 1') 

Answer 3

号见mysql的操作precedence chart。一般来说，如果混合使用AND和OR括号中的内容是个不错的主意。