MySQL行四列

Question

任何人都可以幫助我如何創建一個查詢輸出使用源表上的行數據作爲我的輸出上的標題。請參閱下面的插圖。

E.G.

行數據：

+-----------+-----------+-----------+-----------+ 
| colHeader | value  | no  | price  | 
+-----------+-----------+-----------+-----------+ 
| Header1 | value 1 | no 1  | price1 | 
+-----------+-----------+-----------+-----------+ 
| Header1 | value 2 | no 2  | price2 | 
+-----------+-----------+-----------+-----------+ 
| Header2 | value 1 | no 3  | price3 | 
+-----------+-----------+-----------+-----------+ 
| Header2 | value 2 | no 4  | price4 | 
+-----------+-----------+-----------+-----------+ 

輸出：

+-----------+-----------+-----------+-----------+-----------+ 
| colHeader | value 1 no| value 2 no|value1price|value2price| 
+-----------+-----------+-----------+-----------+-----------+ 
| Header1 | no 1  | no 2 |price1  | price2 | 
+-----------+-----------+-----------+-----------+-----------+ 
| Header2 | no 3  | no 4 |price3  | price4 | 
+-----------+-----------+-----------+-----------+-----------+ 

是否有可能？我想通過PHP

打印它謝謝。

Answer 1

select 
colHeader, 
max(case when value = 'value 1' then no else null end) as value1, 
max(case when value = 'value 2' then no else null end) as value2, 
max(case when value = 'value 1' then price else null end) as value1price, 
max(case when value = 'value 2' then price else null end) as value2price 
from 
your_table 
group by colHeader 

• 看到它在sqlfiddle

執行多個步驟查詢帶電作業是希望自我解釋（增加了一些筆記，雖然）：

select 
* 
from 
t; 

結果：

| COLHEADER | VALUE | NO | PRICE | 
|-----------|---------|------|--------| 
| Header1 | value 1 | no 1 | price1 | 
| Header1 | value 2 | no 2 | price2 | 
| Header2 | value 1 | no 3 | price3 | 
| Header2 | value 2 | no 4 | price4 | 

---

select 
colHeader, 
case when value = 'value 1' then no else null end as value1, 
case when value = 'value 2' then no else null end as value2, 
case when value = 'value 1' then price else null end as value1price, 
case when value = 'value 2' then price else null end as value2price 
from 
t; 

結果：

| COLHEADER | VALUE1 | VALUE2 | VALUE1PRICE | VALUE2PRICE | 
|-----------|--------|--------|-------------|-------------| 
| Header1 | no 1 | (null) |  price1 |  (null) | 
| Header1 | (null) | no 2 |  (null) |  price2 | 
| Header2 | no 3 | (null) |  price3 |  (null) | 
| Header2 | (null) | no 4 |  (null) |  price4 | 

---

不知道下面的步驟是不是比什麼都更加混亂。它返回列colHeader「摺疊」的行。也就是說，如果沒有使用像max()那樣的聚合函數，則顯示每個組的隨機行（在這種情況下，每隔第二行被省略）。請注意，這不是標準的SQL，如果我沒有錯誤，只有MySQL允許這樣做。無論如何，這就是爲什麼我們在最後一步使用max()函數的原因。

select 
colHeader, 
case when value = 'value 1' then no else null end as value1, 
case when value = 'value 2' then no else null end as value2, 
case when value = 'value 1' then price else null end as value1price, 
case when value = 'value 2' then price else null end as value2price 
from 
t 
group by colHeader; 

結果：

| COLHEADER | VALUE1 | VALUE2 | VALUE1PRICE | VALUE2PRICE | 
|-----------|--------|--------|-------------|-------------| 
| Header1 | no 1 | (null) |  price1 |  (null) | 
| Header2 | no 3 | (null) |  price3 |  (null) | 

---

最後一步：

select 
colHeader, 
max(case when value = 'value 1' then no else null end) as value1, 
max(case when value = 'value 2' then no else null end) as value2, 
max(case when value = 'value 1' then price else null end) as value1price, 
max(case when value = 'value 2' then price else null end) as value2price 
from 
t 
group by colHeader; 

結果：

| COLHEADER | VALUE1 | VALUE2 | VALUE1PRICE | VALUE2PRICE | 
|-----------|--------|--------|-------------|-------------| 
| Header1 | no 1 | no 2 |  price1 |  price2 | 
| Header2 | no 3 | no 4 |  price3 |  price4 |