如何將兩個別名添加到通過MySql查詢創建的表中？

Question

我有一個表結構如下：

year 
---------- 
1995 
2000 
2010 

*（前三行）

我想創建一個「差異」列其使用輸入年份：

ind | year | diff 
----------------- 
    1 | 1995 | 0 
    2 | 2000 | 5 
    3 | 2010 | 10 

爲了做到這一點，我試圖創建和ind列和修改這裏建議：http://www.mysqltutorial.org/mysql-tips/mysql-compare-calculate-difference-successive-rows/）

雖然我不成功w第i個給第二別名我已經創建表：

SET @row_number = 0; 

SELECT 
     g1.ind 
    (g2.year - g1.year) AS diff 
FROM (
     select * from 
         (SELECT 
          (@row_number:=@row_number + 1) AS ind, year 
         FROM 
          movies) t 

) g1 
INNER JOIN 
g1 g2 ON g2.ind = g1.ind + 1 

的錯誤是： 錯誤代碼：1146表「db_name.g1」不存在

Answer 1

DROP TABLE IF EXISTS my_table; 

CREATE TABLE my_table 
(year INT NOT NULL PRIMARY KEY); 

INSERT my_table VALUES 
(1995),(2000),(2010); 

例如爲：

SELECT x.year 
    , x.year - COALESCE(MAX(y.year),x.year) diff 
    FROM my_table x 
    LEFT 
    JOIN my_table y 
    ON y.year < x.year 
GROUP 
    BY x.year; 
+------+------+ 
| year | diff | 
+------+------+ 
| 1995 | 0 | 
| 2000 | 5 | 
| 2010 | 10 | 
+------+------+ 
3 rows in set (0.01 sec) 

......或者......

SELECT year 
    , COALESCE(year-@prev,0) diff 
    , @prev:=year 
    FROM my_table 
    , (SELECT @prev:=null) vars 
ORDER 
    BY year; 
+------+------+-------------+ 
| year | diff | @prev:=year | 
+------+------+-------------+ 
| 1995 | 0 |  1995 | 
| 2000 | 5 |  2000 | 
| 2010 | 10 |  2010 | 
+------+------+-------------+ 

Answer 2

我不知道，如果你有點過分複雜的事情。

試試這個：

SELECT 
    m1.id, 
    m1.year, 
    IFNULL(m1.year - m2.year, 0) AS diff 
FROM 
    movies m1 
LEFT JOIN 
    movies m2 ON m2.id +1 = m1.id 
ORDER BY id ASC 

其輸出（使用數據）

|id|year|diff| 
+--+----+----+ 
|1 |1995| 0 | 
|2 |2000| 5 | 
|3 |2010| 10 | 

如果id不存在，也不需要產生，我們只是包裹在m2.year diff字段加上max：

SELECT 
    m1.year, 
    IFNULL((m1.year - max(m2.year)),0) AS diff 
FROM movies m1 
LEFT JOIN 
    movies m2 on m1.year > m2.year 
GROUP BY m1.year 

...然後加入年份。這給：

|year|diff| 
+----+----+ 
|1995| 0 | 
|2000| 5 | 
|2010| 10 |