单桌上的两个连接

Question

我有两张桌子：

Table1
id    acc    offacc    debit    credit
1     43     44        12.2     0

Table2
id    dispval
43    ub01
44    cust02

如何在单行中获取此内容：

id    acc    offacc    debit    credit
1     ub01   cust02    12.2     0

Answer 1

使用表别名

select t1.id, t2a.dispval as acc, t2b.dispval as offacc, t1.debit, t1.credit
from   Table1 as t1
       inner join Table2 as t2a on t2a.id = t1.acc
       inner join Table2 as t2b on t2b.id = t1.offacc

Answer 2

加入的替代方案：

select id,
       (select dispval from Table2 where id = [t1].acc) as acc,
       (select dispval from Table2 where id = [t1].offacc) as offacc,
       debit,
       credit
from Table1 [t1]

Answer 3

考虑在table1上使用两次LEFT JOIN，如下所示

select 
t1.id,
acc=t2.dispval,
offacc=t3.dispval,
t1.debit,
t1.credit
from Table1 t1 left join
     Table2 t2 on t1.acc=t2.id
     Table2 t3 on t1.offacc=t3.id