Question

hi i am using SQL Server 2008, want to create a view to list the different between two tables.

for example

t1
id    name
----  ------
1      John
2      peter
3      mary
4      joe
5      sun

t2
id    name
---   ----
1      john
2      joe

how to create a view to list all the name in t1 but not in t2.

i tried to do that, and always get
“Conversion failed when converting from a character string to uniqueidentifier.”
error

and also, i don`t want to use
select something not in {something}, this is slow

so is there any way can use join??

Answer 1

NOT IN

---

SELECT t1.name
  FROM TABLE_1 t1
 WHERE t1.name NOT IN (SELECT t2.name
                         FROM TABLE_2 t2)

NOT EXISTS

---

SELECT t1.name
  FROM TABLE_1 t1
 WHERE NOT EXISTS (SELECT NULL
                     FROM TABLE_2 t2
                    WHERE t2.name = t1.name)

LEFT JOIN/IS NULL:

---

   SELECT t1.name
     FROM TABLE_1 t1
LEFT JOIN TABLE_2 t2 ON t2.name = t1.name
    WHERE t2.name IS NULL

Summary

---

Contrary to your belief, NOT IN will perform equivalent to NOT EXISTS. LEFT JOIN/IS NULL is the least efficient of the three options.