如何从两个查询的组合中获得有限的行数

Question

我正面临一些逻辑问题。希望有人能给我找到一个解决方案

我有一个查询

select FirstName||'|'||LastName||to_char(salary) 
from (select FirstName,LastName,salary from subs_tbl where salary=24000) 
union all select FirstName||'|'||''||to_char(salary) 
from (select FirstName,LastName,salary from subs_tbl where salary=30000)

所以我的结果是

Satish|Kumar|24000
Vimal|Kumar|24000
Dinesh||30000

假设我的结果是3行，但我需要向整个查询添加另一个条件，即我只需要这些查询组合中的2行。

请帮我处理这个

Answer 1

select FirstName||'|'||LastName||to_char(salary) 
from (select FirstName,LastName from subs_tbl where salary=24000) 
union all select FirstName||'|'||''||to_char(salary) 
from (select FirstName,LastName from subs_tbl where salary=30000) limit 0,2

Answer 2

尝试避免使用的联合

SELECT FirstName||'|'||LastName||to_char(salary) 
FROM subs_tbl 
WHERE salary=24000 or salary=30000) 
LIMIT 2

编辑

SELECT fullname
FROM   (SELECT firstname
           || '|'
           || lastname
           || To_char(salary) AS 'FullName'
    FROM   (SELECT firstname,
                   lastname,
                   salary
            FROM   subs_tbl
            WHERE  salary = 24000)
    UNION ALL
    SELECT firstname
           || '|'
           || ''
           || To_char(salary) AS 'FullName'
    FROM   (SELECT firstname,
                   lastname,
                   salary
            FROM   subs_tbl
            WHERE  salary = 30000))
WHERE  rownum <= 5;

希望这能帮助