php - 从数据库中检索数据作为真实数据

Question

这是我的数据库表。我想将水平键值检索为垂直。

    city_id  cat_id  value
     100      1       1000
     100      2       2000
     101      1        350
     101      2        500
     102      1       1000
     102      2       2000
     103      1         10
     104      2          5

输出:

city_id  catagory1    catagory2
100        1000          2000
101         350           500
102        1000          2000
103          10             0
104           0             5

Answer 1

您需要一个数据透视结果:

select
  city_id, 
  max(case cat_id when 1 then value else 0 end) as category_1,
  max(case cat_id when 2 then value else 0 end) as category_2
from
  my_table
group by
  city_id