February 1, 2012 at 7:52 am
I am trying to analyze the behavior of joins with theta operators. I have created two tables with single column.
t1 t2
-- ---
a b
b c
c d
d e
e f
f g
I ran these queries
1) select t1.col1,t2.col1 from t1 full outer join t2 on t1.col1 <> t2.col1
results:
col1col1
a b
a c
a d
a e
a f
a g
b c
b d
b e
b f
b g
c b
c d
c e
c f
c g
d b
d c
d e
d f
d g
e b
e c
e d
e f
e g
f b
f c
f d
f e
f g
2) select t1.col1,t2.col1 from t1 full outer join t2 on t1.col1 <> t1.col1
col1col1
a NULL
b NULL
c NULL
d NULL
e NULL
f NULL
NULLb
NULLc
NULLd
NULLe
NULLf
NULLg
I am unable to understand how this is getting executed internally.
Can some body explain the internal execution of these T-SQL statements?
February 1, 2012 at 9:02 am
February 1, 2012 at 10:25 am
chowdarysurendranath.c (2/1/2012)
...2) select t1.col1,t2.col1 from t1 full outer join t2 on t1.col1 <> t1.col1
...
t1.col1 <> t1.col1
this clause returns false for every row (is the same as 1 <> 1 or x <> x)
So on for any t1 there's no t2 and vice-versa
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