被淡忘的SQLServer相比运算符谓词

官方的参考文档 %28SQL.90%29.aspx
他们作用于比较运算符和子查询之间,作用类似Exists、not exists、in、not
in以及其他逻辑意义,这些语法同样被SQLServer2000支持但是很少看到有人用它们。
复制代码 代码如下: set nocount on use
tempdb go if (object_id (‘t1’ ) is not null ) drop table t1 create
table t1 (n int ) insert into t1 select 2 union select 3 if (object_id
(‘t2’ ) is not null ) drop table t2 create table t2 (n int ) insert into
t2 select 1 union select 2 union select 3 union select 4 select * from
t2 where n all (select n from t1 ) –4 select * from t2 where n any
(select n from t1 ) –3,4 –select * from t2 where nsome(select n from
t1) –3,4 select * from t2 where n= all (select n from t1 ) –无数据
select * from t2 where n= any (select n from t1 ) –2,3 –select *
from t2 where n=some(select n from t1) –2,3 select * from t2 where n
all (select n from t1 ) –1 select * from t2 where n any (select n from
t1 ) –1,2 –select * from t2 where nsome(select n from t1) –1,2
select * from t2 where n all (select n from t1 ) –1,4 select * from
t2 where n any (select n from t1 ) –1,2,3,4 –select * from t2 where
nsome(select n from t1)–1,2,3,4 set nocount off
注意,如果t1中包含null数据,那么所有All相关的比较运算将不会返回任何结果,原因就不用多解释了。而因为t1和t2表的null的存在他们和not
exists之类的比较符会有一些区别。 比如下面两句 select * from t2 a where
not exists(select 1 from t1 where n=a.n) select * from t2 where n
all(select n from t1)
他们逻辑上意义很像但是对于null的处理却是恰恰相反,第一句会忽略子查询的null而把t2的null同时查出来,第二句却是忽略了t2的null同时会因为t1中的null而无法查询到数据。