How does MySQL query specify conditions and query additional pieces of data?

<code>SELECT * FROM `subject` WHERE  Subject_id IN (1602509) OR  1=1 LIMIT 5
比如数据库里面有一条记录 Subject_id =1602509,我的结果集想查询出5条记录,并且包含
Subject_id =1602509这一条记录,SQL该如何写呢??

如果没有Subject_id =1602509这条记录,那么就用其他数据补齐5条记录</code>

Reply content:

<code>SELECT * FROM `subject` WHERE  Subject_id IN (1602509) OR  1=1 LIMIT 5
比如数据库里面有一条记录 Subject_id =1602509,我的结果集想查询出5条记录,并且包含
Subject_id =1602509这一条记录,SQL该如何写呢??

如果没有Subject_id =1602509这条记录,那么就用其他数据补齐5条记录</code>

<code>SELECT * FROM `subject` WHERE Subject_id IN (1602509) 
UNION 
SELECT * FROM `subject` WHERE Subject_id NOT IN (1602509) LIMIT 5</code>

Actually, this is also okay

It is best to implement it at the business layer