How to handled the null values in WHERE IN condition in mysql

wish help you to fix your issue You can use Group By to do this, but it isn't really clear what you want in the case of multiple matches for one table. You can use a combination of left outer join and inner join to ignore the unwanted booking_table rows:

Select
  t.table_id,
  t.floor_id,
  coalesce(Max(bt.table_status),'free') as table_status,
  max(bt.booking_id) as booking_id,
  max(bt.date) as d
From
  ttable as t
    Left Outer Join (
      Select
        bt.table_id,
        bt.table_status,
        b.booking_id,
        b.date
      From
        booking_table as bt 
          Inner Join
        booking As b
          On b.booking_id = bt.booking_id And b.date = '2012-12-09'
    ) bt On bt.table_id = t.table_id
Where
  t.floor_id = 1
Group By
  t.table_id,
  t.floor_id

Select
  t.table_id,
  t.floor_id,
  coalesce(Max(bt.table_status),'free') as table_status,
  max(b.booking_id) as booking_id,
  max(b.date) as d
From
  booking_table as bt
    Inner Join
  booking b
    On b.booking_id = bt.booking_id And b.date = '2012-12-09'
    Right Outer Join
  ttable as t
    On bt.table_id = t.table_id
Where
  t.floor_id = 1
Group By
  t.table_id,
  t.floor_id

To fix this issue That's just the same as string.Format("Value is {0}", someValue) which will check for a null reference and replace it with an empty string. It will however throw an exception if you actually pass null like this string.Format("Value is {0}", null). However in the case of $"Value is {null}" that null is set to an argument first and will not throw.

like below fixes the issue I have simple MySQL tables (simplified for this question): , This query is behaving correctly. It's equivalent to the following:

SELECT A.name, B.name 
FROM A
LEFT OUTER JOIN B ON B.id = A.id_b
WHERE A.name_ext = 'something'

SELECT A.name, (SELECT B.name FROM B WHERE B.id = A.id_b) AS name_ext
FROM A WHERE name_ext = 'something';

SELECT A.name, B.name 
FROM A
INNER JOIN B ON B.id = A.id_b
WHERE A.name_ext = 'something'

Hope that helps Your WHERE clause is what is causing you not to get any data in your output for March, as it will fail for any row in negocio that has a NULL data value, thus effectively converting the LEFT JOIN into an INNER JOIN and removing rows for any month which has no values in negocio (see the manual). That condition should be moved to the ON condition. You do still need a WHERE clause, but it should be on the date generated from t1 and y. I've assumed your requirement on the 9th of May is to count values from the 9th of February onwards, in which case the required condition is:

WHERE STR_TO_DATE(CONCAT_WS('-', y.year, t1.month, DAY(CURDATE())), '%Y-%b-%d') BETWEEN CURDATE() - INTERVAL 3 MONTH AND CURDATE()

SELECT CONCAT(t1.month, ' ' , y.year) as month, 
       COUNT(t2.id) as quantity
FROM 
(SELECT 1 AS mnum, 'Jan' AS month UNION ALL 
SELECT 2, 'Feb'  UNION ALL 
SELECT 3, 'Mar'  UNION ALL 
SELECT 4, 'Apr'  UNION ALL 
SELECT 5, 'May'  UNION ALL 
SELECT 6, 'Jun'  UNION ALL 
SELECT 7, 'Jul'  UNION ALL 
SELECT 8, 'Aug'  UNION ALL 
SELECT 9, 'Sep'  UNION ALL 
SELECT 10, 'Oct'  UNION ALL 
SELECT 11, 'Nov'  UNION ALL 
SELECT 12, 'Dec' ) t1 CROSS JOIN 
(SELECT DISTINCT YEAR(data) AS year FROM negocio) y 
LEFT JOIN negocio t2 ON t1.mnum = MONTH(t2.data) AND y.year = YEAR(t2.data) AND t2.data BETWEEN CURDATE() - INTERVAL 3 MONTH AND CURDATE()
WHERE STR_TO_DATE(CONCAT_WS('-', y.year, t1.month, DAY(CURDATE())), '%Y-%b-%d') BETWEEN CURDATE() - INTERVAL 3 MONTH AND CURDATE()
GROUP BY y.year, t1.month, t1.mnum
ORDER BY y.year, t1.mnum