lesson

Indexes & Performance

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35 minlesson

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1 min read

Indexes & Performance: Aggregates

Databases use indexes to speed up lookups, but understanding how queries scan data is just as important. COUNT(*) is an aggregate that returns the number of matching rows.

Your Task

Count how many comments have been left on the post titled 'First Post'. Join posts and comments, filter by title, and return the count.

You completed the free preview — you are ready for the full path.

All lessons are readable below. To write and run code from lesson 11 onwards, upgrade to Path Plus ($9/mo) or Pro.

1 min read

Indexes & Performance: Aggregates

Databases use indexes to speed up lookups, but understanding how queries scan data is just as important. COUNT(*) is an aggregate that returns the number of matching rows.

Your Task

Count how many comments have been left on the post titled 'First Post'. Join posts and comments, filter by title, and return the count.

1 min read

Indexes & Performance: Aggregates

Databases use indexes to speed up lookups, but understanding how queries scan data is just as important. COUNT(*) is an aggregate that returns the number of matching rows.

Your Task

Count how many comments have been left on the post titled 'First Post'. Join posts and comments, filter by title, and return the count.

1 min read

Indexes & Performance: Aggregates

Databases use indexes to speed up lookups, but understanding how queries scan data is just as important. COUNT(*) is an aggregate that returns the number of matching rows.

Your Task

Count how many comments have been left on the post titled 'First Post'. Join posts and comments, filter by title, and return the count.