问题描述
我试图在2个表之间创建多对多关系。我有3个表。它遵循TOXY模型。
I am trying to create a many to many relationship between 2 tables. I've got 3 tables for that. It follows TOXY model.
table a: a.id (primary key)
table ab: ab.a_id (foreign key) ab.b_id (foreign key)
table b: b.id (primary key)
我应该如何插入数据，以便将其全部链接起来？
How should I insert the data so it will be all linked up?
这样吗？ INSERT INTO（'name'）VALUES（'my name'）;
INSERT INTO b（'name'）VALUES（'my name'）;
将a.id和b.id放在表ab中。我应该如何检索它们？
but then I have to have the a.id and b.id to put it in table ab. How should I retrieve them?
我知道我可以做一个SELECT a.id FROM WHERE name ='my name'。但是没有一个更简单的方法，当u插入行时，自动返回一个id？
i know i could do a SELECT a.id FROM a WHERE name = 'my name'. but isnt there an easier way for this that automatically returns an id when u INSERT the row?
推荐答案
所有你需要做的是将这些ID存储在变量中以在查询中使用，以插入到 ab 表中。 LAST_INSERT_ID（）返回插入行的ID。所以，在PHP中例如：
All you need to do is store those IDs in variables to use in a query to insert into the ab table. LAST_INSERT_ID() returns the ID of the inserted rows. So, in PHP for instance:
// Run command to insert into A, then:
$a = mysql_query('SELECT LAST_INSERT_ID();');
// Run command to insert into B, then:
$b = mysql_query('SELECT LAST_INSERT_ID();');
// Then $a and $b hold the IDs that you can use to insert into AB.
mysql_query("INSERT INTO ab (a_id, b_id) VALUES ($a, $b);");
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