TSql checksum 比较两个表的数据是否相同

if object_id(‘dbo.ta‘) is not null
    drop table dbo.ta

if object_id(‘dbo.tb‘) is not null
    drop table dbo.tb

create table dbo.ta
(c1 int,
c2 varchar(10)
)
create table dbo.tb
( b1 int,
b2 varchar(10)
)

insert into dbo.ta values(1,‘a‘),(10,‘a0‘),(11,‘a1‘),(12,‘a2‘),(13,‘a3‘),(14,‘a4‘)
insert into dbo.tb values(1,‘a‘),(10,‘a0‘),(11,‘a1‘),(12,‘a2‘),(13,‘a3‘),(14,‘a4‘),(15,‘a5‘)

--use join clause to compare
select *
from dbo.ta a
left join dbo.tb b
on checksum(c1,c2)=checksum(b1,b2)
where b.b1 is null

select *
from dbo.ta a
right join dbo.tb b
on checksum(c1,c2)=checksum(b1,b2)
where a.c1 is null

--use except clause to compare
select checksum(c1,c2) from dbo.ta
except
select checksum(b1,b2) from dbo.tb

--the query resutl is 1779172094
select checksum(b1,b2) from dbo.tb
except
select checksum(c1,c2) from dbo.ta

--use the value to query 
select * from dbo.tb where checksum(b1,b2)=1779172094

-- Create a checksum index
ALTER TABLE Production.Product
ADD cs_Pname AS CHECKSUM(Name);
GO
CREATE INDEX Pname_index ON Production.Product (cs_Pname);
GO

--校验和索引可用作哈希索引，尤其是当要索引的列为较长的字符列时可以提高索引速度。 校验和索引可用于等价搜索。
/*Use the index in a SELECT query. Add a second search 
condition to catch stray cases where checksums match, 
but the values are not the same.*/

SELECT * 
FROM Production.Product
WHERE CHECKSUM(N‘Bearing Ball‘) = cs_Pname
AND Name = N‘Bearing Ball‘;
GO