将两个选择查询合并为一个

Question

我有2个选择查询

select Amount,
       CurrentBalanceCurrency,
       AmountType
from UserBalance
where AmountType= 10

select Amount,
       CurrentBalanceCurrency,
       AmountType
from UserBalance
where AmountType= 20

我想在一行中进行此查询，而无需两次访问数据库。

Answer 1

在IN子句中使用where运算符：

select Amount, CurrentBalanceCurrency, AmountType 
from UserBalance 
where AmountType in (10,20);

Answer 2

您可以使用 IN 运算符。

查询

select [Amount], [CurrentBalanceCurrency], [AmountType]
from [UserBalance]
where [AmountType] in (10,20);

Answer 3

您应该在这两个条件之间使用OR：

select Amount
,CurrentBalanceCurrency
,AmountType 
from UserBalance where AmountType= 10 OR AmountType = 20

Answer 4

另一种选择是使用全部联合连接结果集，在某些情况下，这可以提高或或您必须自己进行测试）：

select Amount,
       CurrentBalanceCurrency,
       AmountType
from UserBalance
where AmountType= 10
union all
select Amount,
       CurrentBalanceCurrency,
       AmountType
from UserBalance
where AmountType= 20