Php 查询包含或不包含值的道具列表
我试图对三个关系表进行Php 查询包含或不包含值的道具列表,php,mysql,select,relational,Php,Mysql,Select,Relational,我试图对三个关系表进行SELECT,如下所示: table_materials -> material_id - material_name table_props -> prop_id - prop_name table_materials_props - row_id -> material_id -> prop_id - prop_value 在我的页面上,我希望得到这样的结果,但我对查询有一些问题: material prop A prop B
SELECT
,如下所示:
table_materials
-> material_id
- material_name
table_props
-> prop_id
- prop_name
table_materials_props
- row_id
-> material_id
-> prop_id
- prop_value
在我的页面上,我希望得到这样的结果,但我对查询有一些问题:
material prop A prop B prop C prop D prop E
wood 350 NULL NULL 84 16
iron NULL 17 NULL NULL 201
copper 548 285 99 NULL NULL
因此,查询应该返回如下内容:
material prop_name prop_value
wood prop A 350
wood prop B NULL
wood prop C NULL
wood prop D 84
wood prop E 16
// and go on with others rows
SELECT *
FROM table_materials AS m
INNER JOIN table_materials_props AS mp
ON m.material_id = mp.material_id
INNER JOIN table_materials_props AS p
ON mp.prop_id = p.prop_id
ORDER BY p.prop_name
我想用一些类似于:
material prop_name prop_value
wood prop A 350
wood prop B NULL
wood prop C NULL
wood prop D 84
wood prop E 16
// and go on with others rows
SELECT *
FROM table_materials AS m
INNER JOIN table_materials_props AS mp
ON m.material_id = mp.material_id
INNER JOIN table_materials_props AS p
ON mp.prop_id = p.prop_id
ORDER BY p.prop_name
问题是查询没有返回NULL
值,我需要所有物料的prop
顺序相同,无论prop值是否为NULL
我希望这个例子是清楚的 交叉连接(或不带条件的内部连接)所有选项,然后将其左连接到关联实体表。即使组合在关联表中不存在,左连接也将保留道具/材质
未经测试:
SELECT *
FROM table_materials AS m
INNER JOIN table_props as p
LEFT JOIN table_material_props AS mp
ON p.prop_id = mp.prop_id
AND
m.material_id = mp.material_id;
ORDER BY p.prop_name
你是否有一个固定的“道具”列表在你的链接表中只有5个,或者这只是一个例子。。。如果修复,您是否希望严格控制“道具”的数量,从而限制创建交叉标签样式的结果?道具的数量可能会增加,因此我决定使用这种结构。