SQLSERVER计算年龄

Question

a表 妇女表 guid：自增长
                  birthday：出生日期
b表 孩子表 id：主键
                  birthday：出生日期
                  personid：母亲，a表外键
怎么查询出子女出生时育龄妇女年龄小于20岁的所有妇女的信息（a表）

Answer 1

select datediff(d,'2008-05-20','2012-01-24')/365
/*
3
*/

Answer 2

select * from A inner join B a.guid=b.personid where datediff(d,b.birthday,a.birthday)/365<20
 

Answer 3

--如果只算年份.
select a.* , 
(select personid , max(birthday) birthday from b group by personid) t
where a.guid = t.personid and datediff(yy,t.birthday,a.birthday) < 20 

Answer 4

declare @妇女表 table (guid uniqueidentifier,birthday varchar(20))
insert into @妇女表
select '76EC96F0-BE70-4648-9491-47DA12D8E351','1976-02-09' union all
select '7ADE50D1-E389-4DC2-965A-D813291338BA','1991-02-09' union all
select 'F08CF424-9B98-4A92-8DFC-7863CB367709','1982-02-09' union all
select 'C48E8450-F8EF-4085-BD4F-76D2F7119FCC','1985-02-09' union all
select '5EBC647C-8AEB-488B-8A19-F7C092D5805A','1979-02-09'declare @孩子表 table (id int,birthday datetime,personid varchar(36))
insert into @孩子表
select 1,'2010-02-12','5EBC647C-8AEB-488B-8A19-F7C092D5805A' union all
select 2,'2009-12-02','7ADE50D1-E389-4DC2-965A-D813291338BA' union all
select 3,'2010-12-02','F08CF424-9B98-4A92-8DFC-7863CB367709' union all
select 4,'2010-12-08','C48E8450-F8EF-4085-BD4F-76D2F7119FCC' union all
select 5,'2009-12-02','76EC96F0-BE70-4648-9491-47DA12D8E351'select a.* from @妇女表 a left join @孩子表 b
on a.guid=b.personid
where datediff(year,a.birthday,b.birthday)<20/*
guid                                 birthday
------------------------------------ --------------------
7ADE50D1-E389-4DC2-965A-D813291338BA 1991-02-09
*/