Easy SQL Analytics Question 36 of 220

What does COUNT(*) return compared with COUNT(column)?

Data Science track · Speak this in 60–90 seconds · Faridabad & Delhi NCR

Without indexScan every row

With indexJump to keys

CostWrites slower

COUNT(*) counts rows, including those with nulls.

Why interviewers care about SQL Analytics:

SQL Analytics questions separate

people who only read docs from people who shipped.

Keep it short, concrete,

and tied to Data Science work.

Stay structured

Name the idea, why it exists, then one short example.

Close cleanly

End with when you use it and one common pitfall.

Before you speak the answer, walk the interviewer through these steps:

1
COUNT(*) counts rows, including
those with nulls.
2
COUNT(column) counts only non-null
values of that column, so it can be smaller.
3
This distinction matters for
sparse fields such as optional survey answers or coupon codes.
4
Give an example
One tiny concrete case you can say aloud.
5
Common mistake
What juniors usually get wrong.
6
Close
When you pick this over the alternative.

Here's a short line you can speak, broken into clear beats:

Say this line

“COUNT(column) counts only non-null values of that column, so it can be smaller.”

Break into beats

COUNTcolumncountsonlynonnull

Speaking order

2987408337471632900

Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.

COUNT(*) counts rows, including those with nulls. COUNT(column) counts only non-null values of that column, so it can be smaller.