Question

我正在尝试编写一些代码来确定在执行其他代码之前，另一个表中是否存在1个表中的2个值。我找到了这些：

select count(1)
from Team
where TeamName IN (select Data FROM CSVTest_Match WHERE Header = 'Home Team');

select count(1)
from Team
where TeamName IN (select Data FROM CSVTest_Match WHERE Header = 'Away Team');

当表Team Team TeamName中存在值时，

都会按预期返回值1。但是，这个：

select count(1)
from Team
where TeamName IN (select Data FROM CSVTest_Match WHERE Header = 'Home Team')
AND TeamName IN (select Data FROM CSVTest_Match WHERE Header = 'Away Team');

当（据我所见）它应该结合前两个查询并返回1时返回0。谁能告诉我我做错了什么？

Answer 1

我认为这种方式更具可读性：

select count(1)
from Team
where TeamName IN (select Data FROM CSVTest_Match WHERE Header in ('Home Team', 'Away Team'))

返回1的方法是解码结果：

select case when count(1) = 0 then 0 else 1 end
from Team
where TeamName IN (select Data FROM CSVTest_Match WHERE Header in ('Home Team', 'Away Team'))

Answer 2

您当前的查询说的是：计算TeamName为Home AND Away team的所有行。将AND替换为OR：一个团队可以是家庭团队或远程团队：

select count(1)
from Team
where TeamName IN (select Data FROM CSVTest_Match WHERE Header = 'Home Team')
OR TeamName IN (select Data FROM CSVTest_Match WHERE Header = 'Away Team');

编辑：快速而又肮脏的方式只返回1：

select CASE WHEN count(1) > 0 THEN 1 ELSE 0 END
from Team
where TeamName IN (select Data FROM CSVTest_Match WHERE Header = 'Home Team')
OR TeamName IN (select Data FROM CSVTest_Match WHERE Header = 'Away Team');

在SQL Server中使用AND命令不给出预期的结果

2 个答案: