Reducing two views into one? - mysql

Question

Good afternoon all,
I am new to mySQL. I have everything working just as I want it, but I could only achieve what I wanted by creating a first view, then referencing it in the final view. I wanted to know whether this is bad practice and will result in slower performance or not? And also, just for learning sake whether it could be all done by using a single view. I have tried and tried but keep getting errors.
First I create this view, which I call intermediate view:
CREATE VIEW intermediate_view AS (
SELECT
freight,
shipping_date,
receiver,
tracking_no,
left(cast(receiver as int), 3) as vendor_id,
DATEDIFF(now(),shipping_date) AS days_in_transit,
CASE
WHEN DATEDIFF(now(),shipping_date) > 5 then "Problem"
WHEN DATEDIFF(now(),shipping_date) < 0 then "Not shipped yet"
ELSE "In transit"
END
AS Status
FROM tracking
);
I'm then creating a final view to join data to it from another another table. My second view is
CREATE VIEW final_view AS (
SELECT
intermediate_view.freight,
intermediate_view.shipping_date,
intermediate_view.receiver,
intermediate_view.tracking_no,
intermediate_view.days_in_transit,
intermediate_view.Status,
vendors.vendor_name
FROM intermediate_view
JOIN vendors
on intermediate_view.vendor_id = vendors.vendor_id
);
Basically, all the second table is doing is matching the first 3 numbers of left(cast(receiver as int), 3), to another table table where those 3 numbers have a corresponding company name. Is there a way to join this in one view?
Hopefully I've explained this well enough! Thanks in advance

Answer 1

your cast will not work in MySQL, so use this
CREATE VIEW final_view AS (
SELECT
t.freight,
t.shipping_date,
t.receiver,
t.tracking_no,
left(cast(t.`receiver` as UNSIGNED), 3) as vendor_id,
DATEDIFF(now(),t.shipping_date) AS days_in_transit,
CASE
WHEN DATEDIFF(now(),t.shipping_date) > 5 then "Problem"
WHEN DATEDIFF(now(),t.shipping_date) < 0 then "Not shipped yet"
ELSE "In transit"
END
AS 'Status',
v.vendor_name
FROM tracking t JOIN
vendors v
on left(cast(t.`receiver` as UNSIGNED), 3) = v.vendor_id
);