具有属性和内部联接的MySQL查询

Question

I have 3 tables and testdata, see below.

How can i get this output doing a query?

Itemname     Name        Address
========================================
Test Item 1  test name 1 test address 1
Test Item 2  test name 2 test address 2

Table Item :

id   Name
========================================
1 - Test Item 1
2 - Test Item 2

Table Itemproperties :

id item_id property_id value
======================================
1  1       1           test name 1
1  1       2           test address 1
1  2       1           test name 2
1  2       2           test address 2

Table Properties :

id name
===========
1  name
2  address

Answer 1

You will need to join the Itemproperties table twice, once for the name and once for the address:

SELECT
  i.name Itemname,
  ip1.value Name,
  ip2.value Address
FROM
  Item i
  JOIN Itemproperties ip1 ON i.id = ip1.item_id AND ip1.property_id = 1
  JOIN Itemproperties ip2 ON i.id = ip2.item_id AND ip2.property_id = 2

Answer 2

One way to do it is to hard code on name and address.

SELECT I.Itemname,IPN.value AS Name, IPA.value AS Address
FROM Item I
LEFT JOIN Itemproperties IPN
ON IPN.item_id=I.id
LEFT JOIN Itemproperties IPA
ON IPA.item_id=I.id
WHERE IPN.property_id=1 AND IPA.property_id=2