Test Series

Question

From the following statements which of them is/are true about SQL

a) All attributes used in the group by clause must appear in the select clause

b) An SQL query can contain a having clause only if it has a group by clause

c) An SQL query can contain a having clause even if it does not have a group by clause

d) Not all attributes used in the group by clause need to appear in the select clause

Comments

b and d

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it depends on sql standard nowa days sqls are more advanced than previous ones.

so if i go with gate  exam means previous ones sqls like 1990s sql then option a and b correct

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i think for gate, we need to follow sql-93 standard.

acc to sql-93, option a & option b are correct.

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b) An SQL query can contain a having clause only if it has a group by clause

d) Not all attributes used in the group by clause need to appear in the select clause

is correct.

Answer 1

Option A :

A group by command need to be applied to some attribute. So minimum of one attribute must be selected using select command.

Option B: 

Having command is used to qualify the group by command.

So having depends on group by.

 

Option  A and B are true!

Comments

Bt according to  the recent sql version , An SQL query can contain a having clause even if it does not have a group by clause

and Not all attributes used in the group by clause need to appear in the select clause