SQL中的条件选择？

我有以下SQL代码：

SELECT eml AS "Email Address"
FROM emailtbl
WHERE DEPT LIKE 'E%'

我的问题是，如果部门以“F”开头，我必须选择传真而不是eml。如果部门以“E”开头，我可以如何选择eml；如果部门以“F”开头，我可以如何选择传真

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谢谢

一个选项是使用

UNION ALL

语句

SELECT eml AS "Entity"
FROM   emailtbl
WHERE  DEPT LIKE 'E%'
UNION ALL
SELECT fax AS "Entity"
FROM   emailtbl
WHERE  DEPT LIKE 'F%'

另一种方法是使用

CASE

语句

SELECT eml AS "Entity"
FROM   emailtbl
WHERE  DEPT LIKE 'E%'
UNION ALL
SELECT fax AS "Entity"
FROM   emailtbl
WHERE  DEPT LIKE 'F%'

SELECT CASE WHEN Dept LIKE 'E%' THEN eml ELSE fax END AS "Entity"
FROM   emailtbl
WHERE  DEPT LIKE 'E%' OR DEPT LIKE 'F%'

这个怎么样

IF (SUBSTRING(@useLike,1,1) = 'E')
BEGIN
    SELECT eml AS "Email Address"
    FROM emailtbl
    WHERE DEPT LIKE @useLike

END
ELSE
BEGIN
    SELECT fax AS "Email Address"
    FROM emailtbl
    WHERE DEPT LIKE @useLike
END

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实际上现在页面已经刷新了；Lieven anwser很酷。你的意思是说以前不是吗？；）