Question

我有3张这样的表：

CREATE table materials
 (id serial primary key not null,
 name varchar(50) not null,
 unit varchar(10) not null default 'шт',
 price decimal(12, 2) not null check (price>0));

CREATE table warehouses 
(id serial primary key not null,
 lastname varchar(25) not null);

CREATE table materials_in_warehouses
 (id_warehouses integer references warehouses(id) on update cascade on delete cascade,
 id_materials integer references materials(id),
 unit varchar(15) default 'шт',
 count integer not null CHECK (count>0),
 lastdate date not null, 
primary key (id_warehouses, id_materials);

我需要选择价格为＆gt;的所有材料。 200，这样：在每个仓库中，该材料的数量> 100。

问题在于我们必须使用这种材料装配所有仓库，而不是任何一种。我没有想法。

例如，我有：

materials 
id     name     price    unit
---    ------   -----    -----
3      Silver   300      kg

warehouses
id     lastname   
----   --------- 
2      Forman
3      Tramp

materials_in_warehouses
id_materials     id_warehouses   count  lastdate
------------     -------------   -----  --------
3                3               300    2015-12-20
3                2               200    2015-12-20

...我希望在我的结果中看到Silver，但是如果我添加到table materials_in_warehouses，其中count是＆lt; 100，因此，银不应该。

这是我的示例查询，但它不适合条件

select materials.name
  , materials.price
  , materials.unit 
from materials
  , materials_in_warehouses 
where price > 200 
 AND id = id_materials 
 AND count > 100;

Answer 1

您可以使用以下子查询解决此问题：

第一种情况，计数＆gt;每个仓库100个

SELECT * FROM materials WHERE id IN (
    SELECT m.id FROM 
        materials_in_warehouses AS mw INNER JOIN 
        materials AS m ON (m.id = mw.id_materials) 
    WHERE 
        m.price > 200 AND 
        mw.count > 100
    GROUP BY id
    HAVING COUNT(*) = (SELECT COUNT(*) FROM warehouses)
);

第二种情况，所有仓库数量的总和＆gt; 100

SELECT * FROM materials WHERE id IN (
    SELECT m.id FROM 
        materials_in_warehouses AS mw INNER JOIN 
        materials AS m ON (m.id = mw.id_materials) 
    WHERE 
        m.price > 200 
    GROUP BY id
    HAVING SUM(mw.count) > 100
);

好的，第三种情况，所有材料的价格＆gt;每个仓库中200 AND 计数＆gt; 100

SELECT m.* FROM 
    materials_in_warehouses AS mw INNER JOIN 
    materials AS m ON (m.id = mw.id_materials) 
WHERE 
    m.price > 200 AND 
    mw.count > 100
GROUP BY id

尽可能简单

Answer 2

您需要首先加入表格并建立关系。

SELECT 
 w.lastname
 , m.name
 , m.price
 , miw.count
FROM materials m
 INNER JOIN materials_in_warehouses miw
   ON m.id = miw.id_materials
 INNER JOIN warehouses w
   ON w.id = miw.id_warehouses

从那里，你可以添加where子句来定位你想要的数据。

WHERE m.price >= 200
  AND miw.count > 100

ORDER也有帮助，但只能查看结果。

  ORDER BY w.lastname, m.name

如果您仍然缺少此时希望看到的记录，则可能是数据问题（您没有在MIW表中定义仓库，或者材料表中缺少材料）。

编辑：如果您考虑上述问题中的数据，并添加更改仓库2的MIW行计数为50，那么将排除该行。您仍会在结果中看到Silver，因为它以您所寻找的数量存在于仓库3中。

Answer 3

试试这个

select * from materials 
inner join  materials_in_warehouses on materials.id = materials_in_warehouses.id_materials
where count>100 and price >200

Postgresql没有想法选择查询

3 个答案: