如何使用MySQL从表中获取特定项目的计数

Question

I have two table data and user. I need to get count of data->value and show only greatest count and user->name.

I tried some query but it's wrong.

SELECT data.value, user.name, data.field, COUNT(*) as count
FROM data 
INNER JOIN user 
ON data.value = user.id 
GROUP BY user.name
HAVING data.field = 'user_id'
ORDER BY count DESC
LIMIT 0,1

DATA

id  order_id   field     value
 1      1      user_id     1
 2      2      user_id     1
 3      3      vehicle_id  1
 4      4      user_id     1
 5      5      vehicle_id  2    
 6      6      user_id     2

USER

id    name  
 1    foo
 2    joo
 3    peter 

Current result is

value   name    field   count   
1       foo     user_id   4 

expecting result is

value   name    field   count   
 1      foo     user_id   3

Answer 1

Use where instead of having .
With where you filter the data. But using having takes all records and filter out complete groups and not single records

SELECT data.value, user.name, data.field, COUNT(*) as count
FROM data 
INNER JOIN user ON data.value = user.id 
WHERE data.field = 'user_id'
GROUP BY data.value, user.name, data.field
ORDER BY count DESC
LIMIT 0,1

Answer 2

You must group not only by user.name, but also by data.field and data.value, then you will get the desired result, see ( sqlfiddle )

SELECT data.value, user.name, data.field, COUNT(*) as count
FROM data 
INNER JOIN user ON data.value = user.id 
GROUP BY data.value, user.name, data.field
HAVING data.field = 'user_id'
ORDER BY count DESC
LIMIT 0,1

Answer 3

You should add filter ond data.field also

SELECT data.value, user.name, data.field, COUNT(*) as count
FROM data 
INNER JOIN user 
ON data.value = user.id  and data.field = 'user_id'
GROUP BY user.name
ORDER BY count DESC
LIMIT 0,1