Get the count and total count joining 2 tables in mysql - mysql

Question

I have 2 tables in the MySQL database :
1.
p_code{
code varchar(10) primary key,
discount decimal(4,2) not null,
valid_till date not null,
daily int not null,
total int non null,
max_amount decimal (6, 2) not null
}
2.
p_user{
code varchar(10) not null,
email varchar(50) not null,
date date not null,
primary key (code, email, date),
foreign key (code) references p_code(code)
}
now I want to get for a code in p_code total how many times an email has been used, total how many time the email has been used today and the details of the code.
I have tried the following query :
SELECT pc.discount, pc.valid, pc.daily, pc.total, pc.max_amount, c.tcount, c.count
FROM p_code AS pc
LEFT JOIN (
SELECT t.code, t.email, t.tcount, p.count
FROM (
SELECT code, email, COUNT( email ) AS tcount
FROM p_user
GROUP BY code, email
) AS t
LEFT JOIN (
SELECT code, email, COUNT( email ) AS count
FROM p_user
WHERE `date` = CURDATE( )
GROUP BY code, email
) AS p ON ( t.code, t.email ) = ( p.code, p.email )
) AS c ON pc.code = c.code
WHERE c.email = ?
AND pc.code = ?
But the problem is that if I do not have any entry for the code and email in the table p_user, it does not return any row.
What I require that it should return all the columns from p_code and 0 and 0 for tcount and count columns.

Answer 1

I think you can simplifiy your query this way, and anyway you'll need to put the condition on the left joined data... in the left join.
SELECT
c.discount,
c.valid,
c.daily,
c.total,
c.max_amount,
count(u.email) as totalCount,
sum(case when u.`date` = CURDATE() then 1 else 0 end) as dailyCount
FROM p_code c
LEFT JOIN p_user u on u.code = c.code and u.email = ?
WHERE c.code = ?
GROUP BY c.discount, c.valid, c.daily, c.total, c.max_amount
You could also do, for the "filter" on email :
WHERE c.code = ? and (u.email is null or u.email = ?)

Answer 2

You need to use the IFNULL function.
IFNULL(expr1,expr2)
If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns
expr2.
You need to modify your query like:
SELECT pc.discount
, pc.valid
, pc.daily
, pc.total
, pc.max
, IFNULL(c.tcount, 0) AS tcount
, IFNULL(c.count, 0) as count
FROM p_code AS pc
...