我如何使用PHP，mysql解决这个问题。 [英] How do I solve this using PHP, mysql.

问题描述

我在数据库中有三个表。第一个表有主键indno（自动增量），第二个表有indno ad外键和sn作为主键（AI），第三个表有sn作为外键，id作为主键（AI）。

我在html中创建了一个表单，并使用php，sql从用户那里插入值。我想编写查询以将之前的结果提取到表单中，以便登录的用户可以更改并更新数据，如果他/她使用的话。



我尝试了什么：



查询中有错误。

i used- SELECT * FROM sailform6，sailform7，sailform8其中indno = $ indno;

和形式我使用的值=

I have three tables in a database. First table has primary key indno(auto increment), second table has indno ad foreign key and sn as a primary key(AI), third table has sn as foreign key and id as primary key(AI).
I made a form in html and and inserted values in that form from user using php,sql. I want to write query to fetch previous result into the form so that the logged in user may change and update the data if he/she whises to.

What I have tried:

There is an error in query.
i used- SELECT * FROM sailform6,sailform7,sailform8 where indno=$indno";
and in the form i used value= ""

推荐答案

indno;

和我使用的形式value =

indno";
and in the form i used value= ""

你需要使用JOINS。



SELECT *

来自sailform6 s6

LEFT JOIN sailform7 s7 ON s6.indno = s7.indno

LEFT JOIN sailform8 s8 ON s6.indno = s8.sn

You need to use JOINS.

SELECT *
FROM sailform6 s6
LEFT JOIN sailform7 s7 ON s6.indno = s7.indno
LEFT JOIN sailform8 s8 ON s6.indno = s8.sn

首先，了解 SQL连接的可视化表示 [ ^ ] <无线电通信/>
后跟多个联接如何工作 [ ^ ]

First, learn about Visual Representation of SQL Joins[^]
followed by How Multiple Joins Work[^]

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