通过删除具有类似条件的查询的“Union All”来优化查询

Question

我在PHP中有以下查询：

$query = "Select 'NOTE' note_type, u.UserName,n.NoteId id,n.NoteText note,
                n.TimeStamp Time_Stamp,u.UserShortCode,i.IssueId,i.ProjectFile_FileId
                from Note n inner join UserNote un
                on n.NoteId = un.Note_NoteId inner join User u 
                on u.UserId = un.User_UserId
                inner join Issue i on i.IssueId = un.Issue_IssueId
                inner join Issue i2 on i.ProjectFile_FileId = i2.ProjectFile_FileId
                and i2.IssueId = ?

        union all

        SELECT 'AUDIT_NOTE' note_type,u.UserName,a.AuditId id,a.AuditNote note,
            a.AuditTimeStamp Time_Stamp,u.UserShortCode,i.IssueId,i.ProjectFile_FileId
            FROM `eoffice`.`audit` a inner join User u
            on u.UserId = a.User_UserId
            inner join Issue i on i.IssueId = a.Issue_IssueId
            inner join Issue i2 on i.ProjectFile_FileId = i2.ProjectFile_FileId
            and i2.IssueId = ?
            order by Time_Stamp asc;";

我希望通过删除 union all 来优化查询，从而缩短它。

以下是必要的表格和相应的字段：

1）注意：NoteId，NoteText，TimeStamp

2） UserNote ：User_UserId，Note_NoteId，Issue_IssueId

3）用户：UserId，UserName，UserShortCode

4）审核：AuditId，AuditNote，Issue_IssueId，User_UserId，AuditTimeStamp

5）问题：IssueId，ProjectFile_FileId

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