How to Return a Flag If Exist Id in Another Table MySQL

How to return a flag if exist ID in another table mysql

This is what you are looking for:

select a.*, b.id_table_a, case when b.id is null then 0 else 1 end as flag 
from tablea a
left join tableb b on a.id = b.id_table_a

setting flag value base on record exist in another table

Just add the condition to print the Y or N flag.

SELECT DISTINCT c.* , IF(d.bId is null, 'Y', 'N')
  FROM tableA c
      LEFT JOIN tableB d ON a.aId = d.aId

select column as true / false if id is exists in another table

use LEFT JOIN Services table, Try this query

SELECT members.id, members.name, 
       IF(services.mid IS NULL, FALSE, TRUE) as services
FROM members
LEFT JOIN services ON (members.id = services.mid)

checking if a value exists in another table within the SELECT clause

Using subquery in SELECT CASE will cost more. Use left join instead like below

    select A.name, 
       CASE WHEN B.name IS NOT NULL
       THEN 'common'
       ELSE 'not common'
       END

    from table1 A
    left join table2 B
    on A.name = B.name

Check if entry in table A exists in table B

SELECT *
FROM   B
WHERE  NOT EXISTS (SELECT 1 
                   FROM   A 
                   WHERE  A.ID = B.ID)

MySQL output all records from table but add flag if value present in another

You can do this with a left outer join:

select u.user_id, u.first_name, u.last_name,
       (c.club_id = 2) as flag
from users u left join
     club c
     on u.user_id = c.user_id;

Note that the flag gets a value of 0 (false) or 1 (true). If you want some other values for the flag, then you will need to use a case statement.

EDIT:

If you simply want the flag for each user, then the easiest way is:

select u.*,
       exists (select 1 from club c where u.user_id = c.user_id and c.club_id = 2) as flag
from users u;

Once again, this produces a 0/1 flag. If you want a different value, then it needs to go into a case.

Alternatively, you could use:

select u.user_id, u.first_name, u.last_name,
       (c.user_id is not null) as flag
from users u left join
     club c
     on u.user_id = c.user_id and c.club_id = 2

How to write a MySQL query that returns a temporary column containing flags for whether or not an item related to that row exists in another table

   SELECT   tu.ID, 
            tu.NAME,
            CASE WHEN tf.ID IS NOT NULL THEN 'true' ELSE 'false' END AS Flagged
      FROM  TABLE_USER tu
            LEFT OUTER JOIN TABLE_FLAGS tf ON tu.ID = tf.ID

SQL query- ID not exist in another table or exist but with all records are in history?

try this:

select * from T1
where ID not in(select ID from T2 where HISTORY_FLG!=1)

SQL Fiddle demo

MySQL: Return only rows in one table where ALL values in one column of another table are the same

You could use a not in a subselect for flag <> 1

SELECT main.id 
from main 
WHERE main.id NOT IN (SELECT secondary.main_id 
                             from secondary WHERE flag <> 1);

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