{"height":"190","width":"100%","version":"1.0","provider_name":"Hatena Blog","provider_url":"https://hatena.blog","html":"<iframe src=\"https://hatenablog-parts.com/embed?url=https%3A%2F%2Fhtn20190109.hatenablog.com%2Fentry%2F2023%2F02%2F09%2F224000\" title=\"\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u30b9\u30ad\u30e3\u30f3\u3067not null\u30ab\u30e9\u30e0\u3092count\u3059\u308b\u5834\u5408\u306e\u30c6\u30fc\u30d6\u30eb\u30eb\u30c3\u30af\u30a2\u30c3\u30d7\u6709\u7121 - HTN20190109\u306e\u65e5\u8a18\" class=\"embed-card embed-blogcard\" scrolling=\"no\" frameborder=\"0\" style=\"display: block; width: 100%; height: 190px; max-width: 500px; margin: 10px 0px;\"></iframe>","published":"2023-02-09 22:40:00","type":"rich","blog_title":"HTN20190109\u306e\u65e5\u8a18","author_url":"https://blog.hatena.ne.jp/HTN20190109/","author_name":"HTN20190109","categories":["DB"],"title":"\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u30b9\u30ad\u30e3\u30f3\u3067not null\u30ab\u30e9\u30e0\u3092count\u3059\u308b\u5834\u5408\u306e\u30c6\u30fc\u30d6\u30eb\u30eb\u30c3\u30af\u30a2\u30c3\u30d7\u6709\u7121","image_url":null,"url":"https://htn20190109.hatenablog.com/entry/2023/02/09/224000","blog_url":"https://htn20190109.hatenablog.com/","description":"MySQL (8.0.31)https://dev.mysql.com/doc/refman/8.0/en/explain-output.html#jointype_index drop table tab1;create table tab1(col1 int primary key ,col2 int ,col3 int not null ); create index ind1 on tab1(col1,col2); explainselect /*+ INDEX(tab1 ind1) */ col1, sum(col2) ,count(col3)from tab1group by co\u2026"}