连接MySQL中的两个表，其中一个表在另一个表中具有多个值

Question

Tools table:

id      tool_nr   
687      2902
745      2456
234      3245

Product Table:

id      tool_id   something
3432     687       123456
4587     745       254786
4411     687       258956 
4741     234       874455 
8745     745       987445

So, tools table id equals product table tool_id.

What I would like:

tool_nr     something
2902        123456
2456        254786
2902        258956
3245        874455
2456        987445

As you can see tools table id may have multiple values in the product table, right know my query is giving me "something" values together separated with commas, but I need to change it and I would like to know what would be the best way to do it?

Answer 1

Try this :

SELECT t.tool_nr, p.something 
FROM Product p 
JOIN Tools t ON p.tool_id=t.id;

Answer 2

$result = mysql_query("SELECT 
                             t.tool_nr, 
                             p.something 
                       FROM tools t 
                       LEFT JOIN products p 
                       ON p.tool_id = t.id");

Answer 3

From what I gather you want to have the same order of elements as it is for products. You could try this command:

$result = mysql_query("SELECT Tools.tool_nr, p.something FROM Product  "
                       ." INNER JOIN Tools"
                       ." ON Product.tool_id = Tools.id"
                       ." ORDER BY Product.id");

It would give you all rows where a tool exists for a given product. If you want to show all products instead and only show the tools where they exist for the appropriate products:

$result = mysql_query("SELECT Tools.tool_nr, p.something FROM Product  "
                       ." LEFT JOIN Tools"
                       ." ON Product.tool_id = Tools.id"
                       ." ORDER BY Product.id");

If instead you want to show all Tools and only those products that exist for these tools:

$result = mysql_query("SELECT Tools.tool_nr, p.something FROM Tools  "
                       ." LEFT JOIN Product"
                       ." ON Product.tool_id = Tools.id"
                       ." ORDER BY Product.id");