Question

我正在this post。

中描述的mysql中实现一个简单的搜索

我的代码与给出的示例非常相似：

SELECT
SUM(((LENGTH(p.body) - LENGTH(REPLACE(p.body, 'term', '')))/4) +
    ((LENGTH(p.body) - LENGTH(REPLACE(p.body, 'search', '')))/6))
AS Occurrences
FROM
    posts AS p
GROUP BY
    p.id
ORDER BY
    Occurrences DESC

运作良好。问题是我只想选择出现次数大于0的行（即显示与搜索有关的行）。

我尝试过添加

WHERE Occurrences>0

制作整个代码块：

SELECT
SUM(((LENGTH(p.body) - LENGTH(REPLACE(p.body, 'term', '')))/4) +
    ((LENGTH(p.body) - LENGTH(REPLACE(p.body, 'search', '')))/6))
AS Occurrences
FROM
    posts AS p
WHERE Occurrences>0
GROUP BY
    p.id
ORDER BY
    Occurrences DESC

但这总是会导致查询错误。我已经尝试了其他WHERE子句进行测试，我发现在尝试使用Occurrences变量时我只会遇到错误。

错误是，正如您所料：

Unknown column 'Occurrences' in 'where clause'

有没有办法做我想做的事情？我宁愿不必选择所有行，然后在php中裁掉我不想要的那些，这看起来非常低效。

Answer 1

试试这个：

SELECT Occurrences FROM (
    SELECT
    SUM(((LENGTH(p.body) - LENGTH(REPLACE(p.body, 'term', '')))/4) +
        ((LENGTH(p.body) - LENGTH(REPLACE(p.body, 'search', '')))/6))
    AS Occurrences
    FROM
        posts AS p
    GROUP BY
        p.id
) AS IQ
WHERE Occurrences > 0
ORDER BY
    Occurrences DESC

Answer 2

您不能在WHERE子句中使用别名，仅在ODER BY和HAVING中的某些SQL方言中使用别名，因此您可以尝试使用HAVING < / p>

SELECT
SUM(((LENGTH(p.body) - LENGTH(REPLACE(p.body, 'term', '')))/4) +
    ((LENGTH(p.body) - LENGTH(REPLACE(p.body, 'search', '')))/6))
AS Occurrences
FROM
    posts AS p
GROUP BY
    p.id
HAVING Occurrences>0
ORDER BY
    Occurrences DESC

有些问题引用in the mysql docs

Mysql搜索查询问题

2 个答案: