What is the intermdiate dataset in this sql?

From: deanbrown3d <deanbrown3d_at_yahoo.com>
Date: 24 Jun 2005 23:45:34 -0700
Message-ID: <1119681934.842441.98290@z14g2000cwz.googlegroups.com>

What is the intermediate dataset built in this statement:

---

update T1
set T1.C1 =
(
  select T2.C1 from T2
  where T1.C2 = T2.C2
  and T1.C3 = 123
)

---

And is there any difference between this one and:

---

update (select * from T1 where C3 = 123) set T1.C1 =
(
  select T2.C1 from T2
  where T1.C2 = T2.C2
)

---

and

---

update T1
set T1.C1 =
(
  select T2.C1 from
  T2 inner join T1
  on T1.C2 = T2.C2
  where T1.C3 = 123
)

---

and

---

update T1
set T1.C1 =
(
  select T2.C1 from
  T2 inner join T1
  on T1.C2 = T2.C2
)
where T1.C3 = 123

---

Thanks for any help. I know there are several people I work with that are unclear on this too.

Thanks

Dean Received on Sat Jun 25 2005 - 01:45:34 CDT