在MySQL选择查询中获取错误1022

Question

I have a simple table i am trying to run a select query on. I keep getting this error. #1022 - Can't write; duplicate key in table '/tmp/mysqltmp/#sql_120f_0'

Here is the table info

And this is the query im trying to run

SELECT COUNT( name ) , CONCAT( userapps.activity,  '/', userapps.class ) 
FROM userapps
GROUP BY name

Answer 1

Weird query; do you want:

  SELECT CONCAT(u.activity,'/',u.class) activity_class, COUNT(u.name) name_count
    FROM userapps u
GROUP BY activity_class