Question

假设我有2列，大小和颜色，表的内容如下：

sizes  colors

large  red
large  green
small  green

如果我想要检索large表中sizes和green表中colors的记录，我会这样做：

$q = "SELECT * FROM tablename WHERE sizes='large' and colors='green'";

但是，如果我只想在行中同时包含large和red来修改green该怎么办？

Answer 1

您似乎需要检查匹配的2行。自联接可能是最简单的方法： -

SELECT *
FROM SomeTable a
INNER JOIN SomeTable b
ON a.sizes = b.sizes
WHERE a.sizes = 'large'
AND a.colors = 'red'
AND b.colors = 'green'

避免使用JOIN，但这只返回大小（你还有其他想要返回的列吗？）： -

SELECT sizes, COUNT(DISTINCT colors) AS colour_count
FROM SomeTable
WHERE sizes = 'large'
AND colors IN ('red', 'green')
GROUP BY sizes
HAVING colour_count = 2

如何检查数据库中的多行

1 个答案: