Considering the two tables below called Orders and OrderLines, how many rows would be returned by this SQL query? SELECT o.Order
ID, ol.OrderLineID FROM Orders AS o LEFT JOIN OrderLines AS ol ON o.OrderID = ol.OrderID ;
1 answer:
Answer:
The query will return four (4) rows
Explanation:
(See attachment below for the table)
The query will return rows where ORDERID is the same on both tables i.e. table ORDERS and ORDERLINES.
The similar rows (on column ORDERID) are 1897 and 87; for table ORDERLINESS and table ORDERS.
But on table ORDERLINESS, there are three rows with 1897 (under ORDERID column).
In total, they have 4 rows in common which are
ORDERID
1897
1897
1897 and
87
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Answer:
<em>866.1 N</em>
Explanation:
The torque on the flywheel = 300 N-m
The force from the hydraulic cylinder will generate a moment on CA about point A.
The part of this moment that will be at point B about A must be proportional to the torque on the cylinder which is 300 N-m
we know that moment = F x d
where F is the force, and
d is the perpendicular distance from the turning point = 1 m
Equating, we have
300 = F x 1
F = 300 N this is the frictional force that stops the flywheel
From F = μN
where F is the frictional force
μ is the coefficient of static friction = 0.4
N is the normal force from the hydraulic cylinder
substituting, we have
300 = 0.4 x N
N = 300/0.4 = 750 N
This normal force calculated is perpendicular to CA. This actual force, is at 30° from the horizontal. To get the force from the hydraulic cylinder R, we use the relationship
N = R sin (90 - 30)
750 = R sin 60°
750 = 0.866R
R = 750/0.866 = <em>866.1 N</em>
