please help

[jzhang0502]

if I want to find a user_id from table 1 which does not exist in the
table 2(possible multiple entries for any user_id). the user_id in
table 2 is a subset from table 1.
if I can not use subquery and minus, how can I do it?
thanks.

[Bill Karwin]

jz********@gmail.com wrote:

if I want to find a user_id from table 1 which does not exist in the
table 2(possible multiple entries for any user_id). the user_id in
table 2 is a subset from table 1.
if I can not use subquery and minus, how can I do it?

Use an outer join. Where there is no match, there you have a user_id
that does not exist in table2.

SELECT t1.user_id
FROM table1 AS t1
LEFT OUTER JOIN table2 AS t2 ON t1.user_id = t2.user_id
WHERE t2.user_id IS NULL;

Regards,
Bill K.

[jzhang0502]

thanks. Bill.
really helpful
Bill Karwin wrote:

jz********@gmail.com wrote:

if I want to find a user_id from table 1 which does not exist in the
table 2(possible multiple entries for any user_id). the user_id in
table 2 is a subset from table 1.
if I can not use subquery and minus, how can I do it?

Use an outer join. Where there is no match, there you have a user_id
that does not exist in table2.

SELECT t1.user_id
FROM table1 AS t1
LEFT OUTER JOIN table2 AS t2 ON t1.user_id = t2.user_id
WHERE t2.user_id IS NULL;

Regards,
Bill K.