Question

I have been on this mysql query for 2 days running. This is the scenario:

I have two tables: users and accounts. There structures below:

$sql="create table if not exists users (
    id bigint(20) not null auto_increment,
    username varchar(255) not null,
    password varchar(255) not null,
    email varchar(255),
    phone varchar(40),
    PRIMARY KEY (id, username))";

$sql="create table if not exists accounts (
    id int not null auto_increment, primary key(id),
    userid int(11) not null,
    type varchar(20) not null, <----- we have two types: bill and pay ------>
    amount varchar(255) not null,
    date_paid datetime not null)";

What I Want To Do:

I want to select the phone numbers of people owing over 10,000 and paid or billed last 14days ago or more.

How do we find people that are owing:

When are you billed (assuming 50, 000) a row is added in the db like this:

insert into accounts (id, userid, type, amount, date_paid) values ('', 'id of the person', 'OWE', 50000, '$date');

When the person makes a pay (assume 20, 000), a row is also inserted:

insert into accounts (id, userid, type, amount, date_paid) values ('', 'id of the person', 'PAY', 20000, '$date');

To get the amount the person is owing:

ALL BILLS – ALL PAYMENTS

What i came up with:

select phone  from users u, accounts a1, accounts a2 where u.id=a1.userid and phone != '' and (((select sum(a1.amount) from a1 where a1.userid=u.id and a1.type='owe') - (select sum(a2.amount) from a2 where a2.userid=u.id and a2.type='pay')) >= 10000) and datediff(NOW(), select max (a1.datetime) as datetime from a1 where a1.userid=u.id) > 14 group by u.id

I have been modifying this query for a long time and the best i get are errors. Some of which are:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near select max (a1.datetime) as datetime from a1 where a1.userid=u.id) > 14 group by

When i remove the last and clause it shows: table db.a2 does not exist.

Please how can i go about this?

Answer 1

Hints:

• it would be better when amount would be an decimal or something
• store the payments with negative amount and you can simply sum over amount to get the balance

get the balance

SELECT u.id, SUM(CASE WHEN type = 'OWE' 
                 THEN CAST(amount AS DECIMAL(10,2)) 
                 ELSE CAST(amount AS DECIMAL(10,2))*-1 END ) as balance
FROM users u
INNER JOIN accounts a ON u.id = a.userid
GROUP BY u.id 
HAVING balance > 10000

check that the phone number has at least 5 character

WHERE CHAR_LENGTH(phone) > 4  

All together + Date

SELECT u.phone, u.id, SUM(CASE WHEN type = 'OWE' 
                 THEN CAST(amount AS DECIMAL(10,2)) 
                 ELSE CAST(amount AS DECIMAL(10,2))*-1 END ) as balance,
             MAX (date_paid) as last_action
FROM users u
INNER JOIN accounts a ON u.id = a.userid
WHERE CHAR_LENGTH(phone) > 4 
GROUP BY u.id 
HAVING balance > 10000 OR DATE_SUB(CURDATE(),INTERVAL 14 DAY) <= last_action