sql - 根据条件连接不同的表

Question

create table [premiumuser] (user_id int, name nvarchar(50));
create table [liteuser] (user_id int, name nvarchar(50));
create table [feature] (id nvarchar(50), user_id int, userkey int);

insert into [premiumuser] select 1, 'stephen';
insert into [premiumuser] select 2, 'roger';

insert into [liteuser] select 1, 'apollo';
insert into [liteuser] select 2, 'venus';

insert into feature select 'Upload content', 1, 1;
insert into feature select 'Create account', 1, 0;
insert into feature select 'View content', 2, 0;

我想查看来自 的数据功能 表而不是 userid我想要 username .
这里的问题是如果 userkey是 0，得到 username来自 liteuser 表，否则来自 高级用户 table 。
数据应该像

'Upload content', 'stephen', 1
'Create account', 'apollo', 0
'View content', 'venus', 0

Answer 1

尝试这个:

select 
    f.id,
        case when userkey=0 then l.name else p.name end as username
from [feature] f
    left join [liteuser] l on l.user_id = f.user_id
    left join [premium user] p on p.user_id = f.user_id