... SELECT b FROM mytable WHERE b = c will give you each row of the
database which has identical b and c values.
... SELECT b FROM mytable AS m2 WHERE m2.b = m1.c will join the two views
of the database together, so if mytable contains
b,c
1,2
2,3
the combined table for this subquery looks like:
SELECT c FROM mytable AS m1 WHERE NOT EXISTS (SELECT b FROM mytable AS m2
WHERE m2.b = m1.c);
SELECT c FROM mytable WHERE NOT EXISTS (SELECT b FROM mytable WHERE b = c);
Sincerely,
Cordialement / Best Regards / Mit freundlichen Grüßen / Cordiali saluti !
, 03 December, 2012 18:26
To: sqlite-users@sqlite.org
Subject: [sqlite] what diffrent with this two sql command?
SELECT c FROM mytable AS m1 WHERE NOT EXISTS (SELECT b FROM mytable AS m2
WHERE m2.b = m1.c);
SELECT c FROM mytable WHERE NOT EXISTS (SELECT b FROM mytable WHERE b =
c
On 12/3/2012 8:26 PM, YAN HONG YE wrote:
SELECT c FROM mytable AS m1 WHERE NOT EXISTS (SELECT b FROM mytable AS m2
WHERE m2.b = m1.c);
SELECT c FROM mytable WHERE NOT EXISTS (SELECT b FROM mytable WHERE b = c);
The second query is equivalent to this:
SELECT c FROM mytable AS m1 WHERE
