题解 | #商品交易(网易校招笔试真题)#

```WITH t AS (
	SELECT
		a.author_id,
		a.issue_id,
		b.issue_type 
	FROM
		answer_tb a
		LEFT JOIN issue_tb b ON a.issue_id = b.issue_id 
	) SELECT
	count( DISTINCT author_id ) num 
FROM
	t 
WHERE
	issue_type = "Career" 
	AND author_id IN ( SELECT author_id FROM t WHERE issue_type = "Education" );