Question

采用这种方式:

SELECT SUM(voc=1) AS s, SUM(voc=2) AS d, SUM(voc=3) AS p FROM `pl`;

但现在我需要修改这一询问,因此,在<代码>voc时,其编号为。

SELECT SUM ( voc = 1 OR voc = 7 OR voc = 3 ) as `s` FROM `pl`;

遗憾的是,上述工作并不恰当,我的理解是,可以使用<编码>CASE,但我对此的了解太小......

Answer 1

SELECT SUM ( CASE WHEN voc = 1 OR voc = 7 OR voc = 3 THEN 1 ELSE 0 END) as `s` FROM `pl`;

<><>UPD>/strong> 如@Raul在评论中所说,WHERE。这样做应当更加有效:

SELECT COUNT(*) AS `s` FROM `p1` WHERE voc IN (1,3,7);

UPD2 Changed Sum s to Count s - thanks to @newtower