Unit b review questions
make sure all answers are in red!
give the circumstances under which the equipment listed must be used, and answer related
questions on another piece of paper.
1. electrical protective ppe (rubber insulating gloves, dielectric footwear)
hazards
utility industry tasks or work areas requiring protective clothing:
2. head protective equipment (hard hats)
hazards: i
utility industry tasks or work areas requiring head protection
what is the difference between type i protection and type il protection in a hard hat?
what is the difference between class e protection and class g protection in a hard hat?
what is the difference between a hard hat and a bump hat?
what defects in a hard hat indicate it should not be used?
3. eye and face protective equipment (safety glasses, goggles face shields)
hazards
utility industry tasks or work areas requiring eye or face protection:
dententive mar should be replaced when

SELECT a.id, ab.age, b.min_coins_needed, b.power

FROM(SELECT code, power, min(coins_needed) AS min_coins_needed

 from Wands

 group by power, code) AS b

JOIN Wands wa

 ON a.coins_needed = b.min_coins_needed AND a.code = b.code AND a.power = b.power

JOIN Wands_property AS ab  

 ON a.code = ab.code  

WHERE ab.is_evil = 0          

ORDER BY b.power desc, ab.age DESC;              

Explanation:  

SELECT statement is used to select the columns id, age, coins_needed and power of the wands that Ron's interested in.

It is required to get the minimum coins_needed so, min() aggregate function is used to return the minimum value of coins_needed. So this is how minimum coins needed for wands with same age and power are attained and the resultant set is given the name of min_coins_needed  using alias. This is then grouped by code and power using GROUP BY because code and age has one to one mapping.

Next the JOIN is used to combine columns from two or more relations. Here Wands and Wands_property are joined to obtain id and age.

WHERE clause is used to filter the wands that are not evil.

ORDERED BY is used to sort in order of power and age, the result obtained. DESC is used to sort the result in descending order of power and age.