PHP MySQL mysql_fetch_assoc，数组键以"as"名称区分 [英] PHP MySQL mysql_fetch_assoc with array keys distinguished by 'as' designations

问题描述

说我做一个像select * from table as t1 LEFT JOIN table as t2 ON t1.id=t2.rank的自联接，然后获取结果以使用mysql_fetch_assoc在php中建立一个数组...然后print_r该数组...有没有办法(不仅是数字，而是使用关联标识符)来区分联接中选择的列和原始列?

Say I do a self-join like select * from table as t1 LEFT JOIN table as t2 ON t1.id=t2.rank, then fetch results to build an array in php using mysql_fetch_assoc... then print_r the array... Is there a way (not just numbers, but using associative identifiers) to distinguish the columns selected in the join, vs the original?

推荐答案

只要使用*通配符，就会发现具有相同名称的列将覆盖关联数组中的相同键.

As long as you are using the * wildcard, you will find columns of the same name will overwrite the same keys in your associative array.

您必须为至少一个表中的列赋予列别名:

You must give column aliases to columns from at least one of the tables:

select t1.*, t2.col1 as t2col1, t2.col2 as t2col2, ...
from table as t1 LEFT JOIN table as t2 ON t1.id=t2.rank

否则，您可以使用通配符，但以行数组的形式获取该行:

Or else you can use the wildcard, but fetch the row as an ordinal array:

$row = mysql_fetch_array($result, MYSQL_NUM);
echo $row[4];

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您的评论:SQL仅具有*通配符，其含义是给定表中的所有列，以其自然名称表示".您必须在逐列的基础上显式地对列进行别名.

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Re your comment: SQL has just the * wildcard meaning "all columns from a given table, by their natural names." You must alias columns explicitly, on a column-by-column basis.

例外:如果您使用SQLite，则有一个 pragma full_column_names 选项结果集返回合格的列名，因此您可以使用*，但是键以表别名为前缀.这是特定于SQLite的非标准SQL.

Exception: If you use SQLite, there's a pragma full_column_names option that makes the result set return qualified column names, so you can use * but the keys come back prefixed with the table aliases. This is SQLite-specific and nonstandard SQL.

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