在MSSQL中使用IF作为外部应用程序

Question

我想在OUTER APPLY中写IF条件.我需要返回多个列,所以我不想写子查询

SELECT name FROM v_users 
OUTER APPLY
(
    IF CAST(reg_date AS DATE)<CAST('03/25/2017' AS DATE)
   SELECT gender,email,age,class FROM tb_register_old WHERE id=v_users.user_id;
ELSE 
   SELECT gender,email,age,class FROM tb_register_new WHERE id=v_users.user_id;
)s

Answer 1

也许是这个？

SELECT name FROM v_users 
OUTER APPLY
(
 SELECT gender,email,age,class 
 FROM tb_register_old 
 WHERE id=v_users.user_id and CAST(reg_date AS DATE)<CAST('03/25/2017' AS DATE)

 UNION ALL  

 SELECT gender,email,age,class 
 FROM tb_register_new 
 WHERE id=v_users.user_id and CAST(reg_date AS DATE) >= CAST('03/25/2017' AS DATE)
)s