how to find date difference from two different table in mys - mysql

Question

I have two tables
1)LEAD TABLE (which have 3 columns)
Lead_ID || Created_Date || Industry
2)ACCOUNTS TABLE (which have 4 columns)
Account_ID||Created_Date|| Revenue_Range|| Lead_ID
How would I get the average number of days between a lead created and an account created

Answer 1

Don't pay attention to mess in data, I just randomly populated it.
Query returns leadId and difference in days between lead.created_date and account.created_date.
Query:
create table Leads
(
leadId int not null,
created_date datetime,
industry varchar(10),
PRIMARY KEY (leadId)
);
create table Accounts
(
accountId int not null,
created_date datetime,
revenue_range varchar(10),
leadId int not null,
FOREIGN KEY (leadId) REFERENCES Leads(leadId)
);
insert into Leads
values
(1, '2020-01-01', 'a'),
(2, '2020-01-02', 'b'),
(3, '2020-01-03', 'c'),
(4, '2020-02-01', 'd'),
(5, '2020-03-01', 'e');
insert into Accounts
values
(1, '2020-01-03', '1k', 1),
(2, '2020-03-10', '2k', 5),
(3, '2020-02-03', '3k', 2);
select
-- l.leadId,
-- l.created_date as LeadCreatedDate,
-- a.created_date as AccountCreatedDate,
-- ABS is used because it returns with minus sign
AVG(ABS(DATEDIFF(l.created_date, a.created_date))) as AvgDifferenceInDaysBetweenCreation
from Leads as l
inner join Accounts as a
on l.leadId = a.leadId;
You can try it out at SQLize Online