there are two tables:
1, user table (id,name,age),
2, profile picture table (id,user_id,image).
purpose: A user can save multiple avatars .
query everyone, and each user record contains all his pictures (if any). The desired query result is: [(name,age, [image,image,image ])]
ask for advice
use the group_concat function separated by commas. Split
in the business code to see which is faster and which is faster
select
a.name,
a.age,
b.image
from as a
left join (select user_id, group_concat(image) as image from group by user_id) as b
on a.id=b.user_id
select
a.name,
a.age
group_concat(b.image) as image
from as a, as b
where a.id=b.user_id
group by a.name, a.age 1, first define an empty array user_info= []
2, and add the contents of the first table user_id,name,age to the array first. You will get [(userid1,name1,age1, []), (userid2,name2,age2, []).], with the empty array behind it to store the image data later.
3, add one match at a time
-sharp
for i in tb_er:
-sharp user_infouserid
for j in user_info:
if i[1] == j[0]:
j[0] = j[3].append(i[2])
is a stupid method, but it can be realized.
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