将表更改为水平的正确 mysql 代码

Question

我试图让下表看起来像这样

当前查询：

SELECT m.typeID, t.typeName, m.quantity, t.description
FROM invTypeMaterials AS m
LEFT JOIN invTypes AS t
ON m.materialTypeID = t.typeID
LEFT JOIN invTypes
ON m.TypeID = t.typeID
WHERE m.typeID = 10039

当前结果

typeID  typeName    quantity    description     
10039   Tritanium   71  The main building block in space structures. A ver...
10039   Pyerite     24  A soft crystal-like mineral with a very distinguis...
10039   Mexallon    1   Very flexible metallic mineral, dull to bright sil...

我正在寻找的是它像这样显示

 typeID     Tritanium   Pyerite  mexallon   description     
10039       71            24        1       Doesn't matter 

我尝试过左连接、外连接、内连接等的组合，但无法使其工作。 我也尝试过 group_concat，我认为这是我需要的，但无法正确设置列

谢谢

编辑：通过使用以下内容，我使该列看起来像我想要的：

SELECT m1.typeID,
SUM(CASE WHEN m1.materialTypeID = 34 THEN m1.quantity ELSE 0 END) AS Tritanium,
    SUM(CASE WHEN m1.materialTypeID = 35 THEN m1.quantity ELSE 0 END) AS Pyerite,
    SUM(CASE WHEN m1.materialTypeID = 36 THEN m1.quantity ELSE 0 END) AS Mexallon,
    SUM(CASE WHEN m1.materialTypeID = 37 THEN m1.quantity ELSE 0 END) AS Isogen,
    SUM(CASE WHEN m1.materialTypeID = 38 THEN m1.quantity ELSE 0 END) AS Nocxium,
    SUM(CASE WHEN m1.materialTypeID = 39 THEN m1.quantity ELSE 0 END) AS Zydrine,
    SUM(CASE WHEN m1.materialTypeID = 40 THEN m1.quantity ELSE 0 END) AS Megacyte,
    SUM(CASE WHEN m1.materialTypeID = 11399 THEN m1.quantity ELSE 0 END) AS Morphite
FROM invTypeMaterials AS m1
WHERE m1.typeID = 10039

结果：

typeID  Tritanium   Pyerite     Mexallon    Isogen  Nocxium     Zydrine     Megacyte    Morphite    
10039   71          24          1           0       0           0           0           0

当我取出“WHERE”子句并尝试将它们全部拉出时，它显示如下：

 typeID     Tritanium   Pyerite     Mexallon    Isogen  Nocxium     Zydrine     Megacyte    Morphite    
18  13989190531     1301687143  261706229   54807927    14277967    4262960     1540121     40701

有任何想法吗？

更新 2：我明白了，GROUP BY 成功了

Answer 1

假设typeName值始终相同，您可以在查询的选择部分使用子查询来获取所需的值。

$sql = "SELECT m.typeID, 
    (SELECT m.quantity FROM invTypes AS t WHERE m.materialTypeID = t.typeID AND t.typeName = 'Tritanium') as Tritanium,
    (SELECT m.quantity FROM invTypes AS t WHERE m.materialTypeID = t.typeID AND t.typeName = 'Pyerite') as Pyerite,
    (SELECT m.quantity FROM invTypes AS t WHERE m.materialTypeID = t.typeID AND t.typeName = 'Mexallon') as Mexallon
FROM invTypeMaterials AS m
WHERE m.typeID = 10039";

Answer 2

我认为 SQL 中没有任何方法可以生成动态列。 如果您可以编写动态 SQL，那么可以，但是在纯 SQL 中，我不这么认为。

如果您愿意对列进行硬编码，那么您可以这样做

SELECT
    m.TypeID,
    MAX(CASE
        WHEN t.typeName = 'Tritanium' THEN m.quantity
        ELSE 0
    END) Tritanium,
    MAX(CASE
        WHEN t.typeName = 'Pyerite' THEN m.quantity
        ELSE 0
    END) Pyerite,
    MAX(CASE
        WHEN t.typeName = 'Mexallon' THEN m.quantity
        ELSE 0
    END) Mexallon
FROM
    [your FROM clause]
WHERE
    [your WHERE clause]
GROUP BY
    m.TypeID;

Answer 3

We have pivot clause in oracle to do similar kind of functionality.
It helps in writing cross tabulation query i.e., we can aggregate results and rotate rows into columns.

tried the below with some sample data:

create table types(typeid number,typename varchar2(20),
quantity number);

insert into types values(1,'xx',11);
insert into types values(1,'yy',121);
insert into types values(1,'zz',113);

delete from types where typeid in(2,3);

select *from
(select typeid,typename,quantity from types)
pivot
(
sum(quantity)
for typename in('xx','yy','zz') 
)


typeid      xx      yy     zz
1           11      121    113