使用同一表格中另一列的值按组插入列

Question

id name count
------------
1  abc
2  xyz
3  xyz
4  xyz

The following query "select count(name) from temp group by name;" gives me:

count(name)
--------
1
3

I want this result to be updated to the column 'count'. To be precise I want my table to look like :

id name count
------------
1  abc   1
2  xyz   3
3  xyz   3
4  xyz   3

Answer 1

You can get those values with a COUNT / GROUP BY. You can do an UPDATE statement which joins your table with the sub query:-

UPDATE temp a
INNER JOIN
(
  SELECT name, COUNT(*) AS name_count
  FROM temp
  GROUP BY name
  ) b
  ON a.name = b.name
SET a.name_count = b.name_count;