(novice to competent) In the following SQL statement why is GROUP BY necessary to obtain the count of each type of house
(Assuming a table called houses, with columns (house_type, house_id, house_address))
SELECT house_type, count(*) FROM houses GROUP BY house_type;
A) Otherwise the count(*) function would return an error
B) Actually included it would lead to only one result showing the total count of rows in the houses table and a random value in the house_type column
C) It’s needed to run the count(*) function only on the subset of rows which have the same house_type value
D) the above statement is not SQL-92 compliant
(competent to expert)
Will the following SQL statements give the same results:
(assuming a table called surveys which columns (plot, record_id, species))
i – SELECT plot, count(*) FROM surveys GROUP BY plot;
ii – SELECT plot “plot_id”, count(*) FROM surveys GROUP BY plot_id;
A) NO – column aliasing cannot be used in a GROUP BY statement; you have to use the original column name
B) YES – column aliasing can be used in this way and i & ii will give the same results
C) NO – although you can use column aliasing in this way you are mean’t to say – plot AS plot_id – and the use of – plot “plot_id” – is not legal
D) NO – as i is not SQL-92 compliant