How should I practice Block Transaction Count Trends?

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Block Transaction Count Trends

Chainalysis● MediumFULLTIMEONSITE INTERVIEW

Problem statement

The btc_blocks table records one Bitcoin block per row with its height and transaction count.

For every block, show its block_height, current transaction_count, and the preceding block row's transaction count as previous_transaction_count. Add a trend label: Increased, Decreased, or Same by comparing the current count with the previous count.

Order rows by block_height ascending. For the earliest block, return NULL as the previous count and Same as the trend.

Table schema

MySQLPostgreSQLPandas

Use the same input data with any supported language. Open the Schema tab in the editor to see the generated SQL setup or Pandas DataFrames.

btc_blocks

Bitcoin blocks and their transaction counts.

Column	Type	Nullable	Description
block_heightPK	Integer	No	Unique Bitcoin block height.
transaction_count	Integer	No	Number of transactions in the block.

Expected result

Your query or function must return these columns.

Column	Type	Nullable	Description
block_height	Integer	No	—
transaction_count	Integer	No	—
previous_transaction_count	Integer	Yes	—
trend	Text	No	—

Row order: must match exactly. Numeric tolerance: 0.

Constraints

btc_blocks contains from 1 through 2,000 rows.
block_height is a unique nonnegative integer.
transaction_count is a nonnegative integer.
The previous block means the preceding available row after sorting by block_height, even when heights are not consecutive.