如何获取用户ID不在表记录中的所选行mysql

Question

How get selected rows where user id is not in table record

the table like this

table_a

id subid userid
1  2     123
2  4     123

table_b

id title
1  like
2  liked
3  bookmark
4  bookmarked

i use join table to get the result if WHERE userid=123 then get result

id title
2  liked
4  bookmarked

the query

select b.id,b.title from
table_a a
LEFT JOIN table_b b
ON b.id = a.subid
WHERE a.userid = '123'

but, how if userid = '345' and not in table_a get the result too?.. the result is must like this (selected rows)

id title
1  like
3  bookmark

Thankyou

Answer 1

尝试使用此查询从（b.no = a.no）的连接b上选择a.no，b.title，其中a.userid ='345'

Answer 2

You can use the following query:

SELECT id, title FROM t2 LEFT JOIN t1 ON t1.subid = t2.id 
WHERE (t1.userid = 345 AND NOT userid IS NULL) OR (
    NOT EXISTS(SELECT userid FROM t1 WHERE userid = 345) AND userid IS NULL
);

The working examples you can find here: http://sqlfiddle.com/#!9/c6a446/25

Answer 3

You can use left join and get the data for the table where their is no match. I have solved this recently. Chk this link: Least Popular Event - Get list of events where bookings IS NULL OR LEAST

In mysql

SELECT b.no,b.title FROM a LEFT JOIN b ON a.subid = b.no and where a.userid IS NULL;

SELECT b.no,b.title FROM a LEFT JOIN b ON a.subid = b.no and where a.userid <> '345';

in laravel : $least = bmodel::leftJoin('a', function($join) { $join->on('a.subid', '=', 'b.no'); }) ->select('b.no','b.title') ->whereNull('a.userid') ->first(); or get()

You can use this query to get one or more results. It basically compares userid column with no column and gets list of no and title where there is no match in table a.

Answer 4

This basically would select with given userId or if that is not present it then selects the result which

 SELECT * FROM t2 LEFT JOIN t1 ON t1.subid = t2.id WHERE     t1.userid = 123|| 
 (select  userid from t1 where userid =123LIMIT 1) is  null

This is the second case where you will get all the rows where it is not 123 or any number

 SELECT * FROM t2 LEFT JOIN t1 ON t1.subid = t2.id WHERE     t1.userid = 345 || 
 (select  userid from t1 where userid =345 LIMIT 1) is  null