开发者

Difference between 2 selects in SQL

I have one data table:

--------------------
ID |  user | Value
--------------------
1  |  1    | 1
--------------------
2  |  1    | 2
--------------------
3  |  2    | 3
--------------------
4  |  2    | 2
--------------------
5  |  3    | 4
--------------------
6  |  3    | 2
--------------------

I would like to SELECT all rows where value is different comparing to user 1 so the result would be rows with IDs 3 (value is 3) and 5 (value is 2)

I would do something like this (will call it A)

开发者_开发知识库SELECT * FROM table WHERE user = 1

and get all the rows from user 1. Than I would select (will call it B)

SELECT * FROM table WHERE user != 1

and get all other rows. And than I would compare them WHERE A.value != B.value.

I'm stuck on how to merge everything together...

Please help!


Try this:

SELECT * 
FROM table
WHERE value NOT IN ( SELECT value FROM table WHERE user = 1)


The relational operator is indeed 'difference', Oracle has the keyword MINUS, Standard SQL has the keyword EXCEPT e.g.

SELECT value 
  FROM table 
EXCEPT
SELECT value 
  FROM table 
 WHERE user = 1;

Sadly, MySQL doesn't have any such an operator, you have to use other SQL constructs e.g. NOT IN <table expression>:

SELECT value 
  FROM table
 WHERE value NOT IN ( SELECT value
                        FROM table
                       WHERE user = 1 );


select * from table where value not in (select value from table where user = 1);

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