php 在 MySQL 中选择单行
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/1412665/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Selecting a single row in MySQL
提问by aggitan
I am using MySQL, I have a table that has 9 columns. One of them is the primary key.
我正在使用 MySQL，我有一个有 9 列的表。其中之一是主键。
How can I select a single row, by the primary key or column 8 or 4?
如何通过主键或第 8 或 4 列选择单行？
回答by ChristopheD
If I understand your question correctly:
如果我正确理解你的问题：
SELECT * FROM tbl WHERE id = 123 OR colname4 = 'x' OR colname8 = 'y' LIMIT 1
The 'LIMIT' keywordmakes sure there is only one row returned.
在“限价”关键字可以确保只有一个返回行。
回答by RedFilter
select *
from MyTable
where MyPrimaryKey = 123
回答by Ian Clelland
Columns in SQL don't have a defined 'order'. Database systems generally keep track of an order for display purposes, but it doesn't make sense to ask a database to select a column by number. You need to know the column's name in order to query its contents.
SQL 中的列没有定义的“顺序”。数据库系统通常为了显示目的而跟踪顺序，但要求数据库按数字选择列是没有意义的。您需要知道列的名称才能查询其内容。
The same thing goes for the primary key (which, incidentally, may not be just a single column). You have to know which column it is, and what that column is named, in order to execute a query.
同样的事情也适用于主键（顺便说一下，它可能不仅仅是一列）。您必须知道它是哪一列，以及该列的名称，以便执行查询。
If you don't know these things, or need to figure them out dynamically, then
如果你不知道这些东西，或者需要动态地弄清楚，那么
DESCRIBE tablename;
will tell you the names of each column, and whether it is part of the primary key or not. It will return a table that you can read, like any other result.
会告诉你每列的名称，以及它是否是主键的一部分。它将返回一个您可以阅读的表，就像任何其他结果一样。
