Question

我有一张这样的表：

Name    CPP  Java  Python Age

David    1    1     0     40

Mike     1    0     1     50

我想为每个非零CPP / Java / Python值生成一行，并清除其他非零值：

Name    CPP  Java  Python Age

David    1    0     0     40

David    0    1     0     40

Mike     1    0     0     50

Mike     0    0     1     50

我该怎么做？

Answer 1

这应该是魔术：

SELECT name, cpp, 0,0, Age FROM table WHERE cpp = 1 UNION ALL
SELECT name, 0, Java,0, Age FROM table WHERE Java = 1 UNION ALL
SELECT name, 0, 0,Python, Age FROM table WHERE Python = 1

Answer 2

简单的方法是建立联盟，例如，

SELECT name, cpp, 0 as java, 0 as python, age
FROM {table}
WHERE cpp = 1
UNION ALL 
SELECT name, 0 as cpp, java, 0 as python, age
FROM {table}
WHERE java = 1
UNION ALL
SELECT name, 0 as cpp, 0 as java, python, age
FROM {table}
WHERE python = 1

Answer 3

我想你想做的是这样的事情：

SELECT t.Name,t.CPP,t.Java,t.Python,t.Age FROM(
  SELECT Name, CPP, 0 AS Java, 0 AS Python, Age Where CPP = 1
  UNION  
  SELECT Name, 0 AS CPP, Java, 0 AS Python, Age Where Java = 1
  UNION  
  SELECT Name, 0 AS CPP, 0 AS Java, Python, Age Where Python = 1 ) t
ORDER BY t.Name ASC;

希望这有帮助。

如何在SQL中将一行转换为多行

3 个答案: