Group by

Question 1

single row function

Answer 1

when we give 4 i/p we get 4 o/p (allow dupliactes)

Question 2

Group BY

Answer 2

when we give 4 i/p we get 1 o/p ( don’t allow dupliactes). used to group the identical data together.

Question 3

types of group by function

Answer 3

max , min , avg , count & sum

Question 4

max in group by function

Answer 4

this will give 1 max value present in column

Question 5

MAX example

Answer 5

select max (column) from table name

Question 6

MIN in group by function

Answer 6

this will give 1 min value present in column

Question 7

MIN example

Answer 7

select min (column) from table name

Question 8

avg in group by function

Answer 8

this will give 1 average value present in column. We get decimal also.

Question 9

How can we remove the decimal part from the average

Answer 9

round(avg(column))

Question 10

avg eg

Answer 10

select round(avg(column)) from table_name

Question 11

Count in group by function

Answer 11

count the number of records in the column. (Column (*))

Question 12

will count group by function have null

Answer 12

yes

Question 13

count (*)

Answer 13

where * return all column if no confition is specified over there.

Question 14

sum in group by function

Answer 14

this will sum all the column values.

Question 15

what us agregate column

Answer 15

if some action is performed on the column then we call it as agregated column

Question 16

examples of agregates column

Answer 16

min, max , sum , count & avg

Question 17

What happens if we don’t run a grouping function on a column

Answer 17

If we don’t run a grouping function on a column, then we need to add that column in the ‘group by’ clause.

Question 18

should we mention aggregate column in group

Answer 18

no , we mention only non agrregate

Question 19

can we perform any action on aggregate column

Answer 19

yes , using having clause. It’s similar to the ‘where’ clause, but it works on aggregated data.

Question 20

to print non duplicates we use

Answer 20

distinct , group by

Question 21

amiguity

Answer 21

we get this when we have same column in both table

Question 22

how to solve amiguity

Answer 22

we can by specifying the table name before column name (tablename.columnname)

Question 23

can we have any short cut for writing the whole name of table multiple times

Answer 23

yes using aliases. Tablename a (a is aliases where it can be any thing)

Question 24

What is aliasing

Answer 24

Aliasing is a technique in SQL where we give a temporary name to a table or a column in a table. It is used to make column names more readable.

Question 25

How can we filter null values

Answer 25

‘is not null’ condition to filter null values.