Apple SQL Interview Question for Data Scientists and Data Analysts (StrataScratch 9896)

[@AkashRana1111]

Great Videos Frederik and amazing explanation. I think this question can also be solved using left join, in case of large tables performance of join superceds to `not in` query. Select c.first_name From customers c left join orders o on c.id = o.cust_id where o.cust_id is Null

[@frederikmuller]

thanks for adding your solution and calling out possible performance improvements!

[@seanwayland]

I think the Join answer is faster than the nested query.

[@SACHINKUMAR-px8kq]

Thankyou so much sir

[@HolaMexicoo]

in this exampe, does the distinct keyword make any difference to whether the answer is right.

[@frederikmuller]

it won't make a difference to the solution being accepted but using distinct will make the sub-query more efficient as it doesn't pull duplicate rows

[@nehadhami61]

For left join why do we need to specify WHERE condition. Left join will be automatically displaying only the data which is only in "customers" table .

[@pjtarheel]

That’s not correct. Left join includes all records in the left table AND records with a match in the right table.

[@frederikmuller]

@@pjtarheel exactly. filtering to WHERE right_table.field IS NULL after left joining essentially checks for having no matches in the right table.

[@NabeelSher]

Great show

[@frederikmuller]

Thanks!