mysql行转列练习

select key_a,key_b,
max(case field_key when 'test1' then field_name else '' end) as test_1_field_name,
max(case field_key when 'test2' then field_name else '' end) as test_2_field_name
from object_field
group by key_a,key_b

5大聚合函数：

• sum()和avg()用于数值类型
• max()和min()可用于任意类型
• count()分组记录数