add a new entry if doesn't exist in mysql table - sql

Question

I have a table of below structure.
mysql> desc depot;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| recd | date | YES | | NULL | |
| id | int(11) | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
Currently I have records in the below manner.
mysql> select * from depot;
+---------------------+------+
| recd | id |
+---------------------+------+
| 2012-07-09 | 33 |
| 2012-07-11 | 32 |
| 2012-07-15 | 32 |
+---------------------+------+
3 rows in set (0.00 sec)
I need the records to print the query in the below manner, keeping the missed entries of dates of a month (say July-01 to July-31) and having 0 to the value id corresponding missed dates.
select < a magical query >;
+------------+------+
| recd | id |
+------------+------+
2012-07-01 0
2012-07-02 0
2012-07-03 0
2012-07-04 0
2012-07-05 0
2012-07-06 0
2012-07-07 0
2012-07-08 0
2012-07-09 33
2012-07-10 0
2012-07-11 32
2012-07-12 0
2012-07-13 0
2012-07-14 0
2012-07-15 32
2012-07-16 0
2012-07-17 0
2012-07-18 0
2012-07-19 0
2012-07-20 0
2012-07-21 0
2012-07-22 0
2012-07-23 0
2012-07-24 0
2012-07-25 0
2012-07-26 0
2012-07-27 0
2012-07-28 0
2012-07-29 0
2012-07-30 0
2012-07-31 0

Answer 1

You obviously need a second table with a list of possible dates and then you should select from that table with a left join to the one you already have.

Answer 2

A calendar table makes your query and your life easier. In standard SQL this query will give you what you're looking for.
select c.cal_date, coalesce(d.id, 0) id
from calendar c
left join depot d on d.recd = c.cal_date
where c.cal_date between '2012-07-01' and '2012-07-31'
order by c.cal_date
A minimal calendar table just needs a date column.
create table calendar (
cal_date date primary key
);
insert into calendar values
('2012-07-01'),
('2012-07-02'),
...
('2012-07-31');
Instead of writing INSERT statements, you can generate data with a spreadsheet or a scripting program, and load the rows through your database's bulk loader.
I've also written about a more useful calendar table on StackOverflow.

Answer 3

Thanks mates!! I was ambitious on any SQLs if existing. But yeah its reluctant procedure..
Found a workaround as it was clinging long time
BASE TABLE
CREATE TABLE `deopt` (
`recd` datetime DEFAULT NULL,
`id` int(11) DEFAULT NULL
) ENGINE=InnoDB;
Seed records to the base table
insert into deopt values ('2012-07-09 23:08:54',22);
insert into deopt values ('2012-07-11 23:08:54',22);
insert into deopt values ('2012-07-11 23:08:54',2222);
insert into deopt values ('2012-07-12 23:08:54',22);
insert into deopt values ('2012-07-14 23:08:54',245);
Create a table for dates of a month
CREATE TABLE seq_dates
(
sdate DATETIME NOT NULL,
);
Create a Stored Procedure to create records for a called month
delimiter //
DROP PROCEDURE IF EXISTS sp_init_dates;
CREATE PROCEDURE sp_init_dates (IN p_fdate DATETIME, IN p_tdate DATETIME)
BEGIN
DECLARE v_thedate DATETIME;
TRUNCATE TABLE seq_dates;
SET v_thedate = p_fdate;
WHILE (v_thedate <= p_tdate) DO
INSERT INTO seq_dates (sdate)
VALUES (v_thedate);
SET v_thedate = DATE_ADD(v_thedate, INTERVAL 1 DAY);
END WHILE;
END;
delimiter ;
Call the procedure for July month with starting and ending values to be seeded to seq_dates table.
call sp_init_dates ('2012-07-01','2012-07-31');
RESULT QUERY - To fetch records of all dates in a month and its corresponding ids keeping 0 inplace of null for ids.
select date(seq_dates.sdate),coalesce (deopt.id,0) from seq_dates LEFT JOIN deopt ON date(deopt.recd)=date(seq_dates.sdate);
+-----------------------+-----------------------+
| date(seq_dates.sdate) | coalesce (deopt.id,0) |
+-----------------------+-----------------------+
| 2012-07-01 | 0 |
| 2012-07-02 | 0 |
| 2012-07-03 | 0 |
| 2012-07-04 | 0 |
| 2012-07-05 | 0 |
| 2012-07-06 | 0 |
| 2012-07-07 | 0 |
| 2012-07-08 | 0 |
| 2012-07-09 | 22 |
| 2012-07-09 | 22 |
| 2012-07-10 | 0 |
| 2012-07-11 | 22 |
| 2012-07-11 | 2222 |
| 2012-07-11 | 22 |
| 2012-07-11 | 2222 |
| 2012-07-12 | 22 |
| 2012-07-13 | 0 |
| 2012-07-14 | 245 |
| 2012-07-15 | 0 |
| 2012-07-16 | 0 |
| 2012-07-17 | 0 |
| 2012-07-18 | 0 |
| 2012-07-19 | 0 |
| 2012-07-20 | 0 |
| 2012-07-21 | 0 |
| 2012-07-22 | 0 |
| 2012-07-23 | 0 |
| 2012-07-24 | 0 |
| 2012-07-25 | 0 |
| 2012-07-26 | 0 |
| 2012-07-27 | 0 |
| 2012-07-28 | 0 |
| 2012-07-29 | 0 |
| 2012-07-30 | 0 |
| 2012-07-31 | 0 |
+-----------------------+-----------------------+
35 rows in set (0.00 sec)