sql 中 and or

select count(distinct(uid)) from pwd_act_user where year=2013 and month=09 and day=29 and vid=1154 or vid=1162;

134145

查的是  year=2013 and month=09 and day=29 and vid=1154   或者 vid=1162 的用户数

select count(distinct(uid)) from pwd_act_user where year=2013 and month=09 and day=29 and (vid=1154 or vid=1162);
132880

查的是 year=2013 and month=09 and day=29 and vid=1154 或者  year=2013 and month=09 and day=29 and  vid=1162

另有or和and的sql最好多用括号，别吝啬，这样看起来也清晰明白，下面的教训惨痛：

select year, month, day, count(*) 
FROM table
where  ( year='2013' and month=12 and day=02 ) or
 ( year='2013' and month=12 and day=03 ) or  ( year='2013' and month=12 and day=04 ) or
 ( year='2013' and month=12 and day=05 ) or  ( year='2013' and month=12 and day=06 ) or
 ( year='2013' and month=12 and day=07 ) or  ( year='2013' and month=12 and day=08 ) 
AND SID IN (25, 90)  group by  year,month,day;

2013    12      02      103258003
2013    12      03      94857108
2013    12      04      108052348
2013    12      05      105315389
2013    12      06      118105464
2013    12      07      128773299
2013    12      08      2494263

select year, month, day, count(*) 
FROM table
where ( ( year='2013' and month=12 and day=02 ) or
 ( year='2013' and month=12 and day=03 ) or  ( year='2013' and month=12 and day=04 ) or
 ( year='2013' and month=12 and day=05 ) or  ( year='2013' and month=12 and day=06 ) or
 ( year='2013' and month=12 and day=07 ) or  ( year='2013' and month=12 and day=08 ) )
AND SID IN (25, 90)  group by  year,month,day;

2013    12      02      2135578
2013    12      03      1931884
2013    12      04      2128356
2013    12      05      2097469
2013    12      06      2326889
2013    12      07      2524302
2013    12      08      2494263

因为这个浪费了很多时间，真不值得