Doctrine2的查询构建器子字符串辅助方法的正确语法 [英] Correct syntax for Doctrine2's query builder substring helper method

问题描述

好的，这个问题可能是由于我对查询构建器帮助程序的模糊理解，但对于我的生活，我找不到使用substring方法的正确方法。

Ok, this problem is probably due to my foggy understanding of the query builder helper methods but for the life of me I cannot find the correct way to use the substring method.

我正在尝试返回以指定的字母数字值开头的所有结果。以下代码不会抛出任何错误，但也不会返回任何结果。我已经挖了谷歌，但显然几乎没有显示如何使用子字符串。我想让这个在查询构建器中工作，但是我可能需要去DQL或者是raw sql。

I am attempting to return all results that begin with a specified alphanumeric value. The below code does not throw any errors but it also does not return any results. I have scoured google but apparently there is almost nothing showing how to use substring. I would like to get this working in query builder but I may have to go DQL or raw sql.

    $qb->select('p', 't');
    $qb->from('ContentParent', 'p');
    $qb->join('p.titleCurrent', 't');
    $qb->where(
            $qb->expr()->eq($qb->expr()->substring('t.sortTitle', 0, 1), ':letter')
        );

谢谢！

推荐答案

SUBSTRING需要以一个为基础。

SUBSTRING needs to be one-based.

MySQL手册指出：

对于所有形式的SUBSTRING（）
中第一个字符的位置是要从中提取子串的字符串，计算为
1。

For all forms of SUBSTRING(), the position of the first character in the string from which the substring is to be extracted is reckoned as 1.

使用 Oracle ：

SELECT SUBSTR('ABCDEFG',3,4) "Substring"
     FROM DUAL;

Substring
---------
CDEF

从 Transact-SQL手册：

SELECT LastName, SUBSTRING(FirstName, 1, 1) AS Initial
FROM Person.Person
WHERE LastName like 'Barl%'
ORDER BY LastName

从这些示例中可以看出，他们也使用one- （Oracle，但是，当给定 0 ）时，Oracle将承担 1 。

You can see from these examples that they, too, are using one-based (Oracle, however, will assume 1 when given 0).

只需将子串参数更改为't.sortTitle'，1，1 即可正确。

Simply change your substring parameters to 't.sortTitle', 1, 1 and it will work correctly.

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