Question

我有一个mysql表，我喜欢在上面执行查询。我的表格如下：

    date        activity    amount 
    --------    ------      -------- 
    day 1       drink       0 
    day 1       eat         1 
    day 1       breath      1 
    day 2       drink       0 
    day 2       eat         0 
    day 2       breath      0 
    day 3       drink       1 
    day 3       breath      0 
    day 4       eat         1 
    etc          
    etc          
    etc

我想做的是看看吃什么时间是1，而事实上，我希望显示那些日子里的所有活动

//What I was doing right now is:

$activityarray = array();



$result = mysql_query("SELECT * FROM table WHERE activity='eat' AND amount='1'");
$row = mysql_fetch_assoc($result);

//this returns all rows where activity=eat and amount=1


do{
     //perform for each result row a new query; look for the 'date'=$row[date] from the first query and show all activities that have been done that day (activity=1)

     $result2 = mysql_query("SELECT * FROM table WHERE date='".$row[date]."'");
     $row2 = mysql_fetch_assoc($result2);

     do{
         array_push($activityarray,$row2['activity']);
     }while($row2 = mysql_fetch_assoc($result2));

}while($row = mysql_fetch_assoc($result));


print_r($activityarray);

由于每天有数千天和数十项活动，这对我来说似乎不是最有效的方法。有一种方法可以通过一个查询提高效率吗？（所以：检查所吃的日子的所有活动= 1）。希望有人能帮帮我！

Answer 1

使用自我加入：

SELECT t1.*
FROM table AS t1
JOIN table AS t2 ON t1.date = t2.date
WHERE t2.activity = 'eat' AND t2.amount = 1

Answer 2

我的建议，特别是如果您有加入尺寸限制：

select *
from table as t1
where exists (
    select 1
    from table as t2
    where t2.date = t1.date
    and t2.activity = 'eat'
    and t2.amount = 1
    )

PHP＆＃34;数组查询＆＃34; /多个查询

2 个答案: