A cool standard SQL:2003 feature is the aggregate FILTER clause, which is supported natively by at least these RDBMS: ClickHouse CockroachDB DuckDB Firebird H2 HSQLDB PostgreSQL SQLite Trino YugabyteDB The following aggregate function computes the number of rows per group which satifsy the FILTER clause: SELECT COUNT(*) FILTER (WHERE BOOK.TITLE LIKE 'A%'), COUNT(*) FILTER (WHERE … Continue reading Emulating SQL FILTER with Oracle JSON Aggregate Functions
Tag: FILTER
The Performance Impact of SQL’s FILTER Clause
I've found an interesting question on Twitter, recently. Is there any performance impact of using FILTER in SQL (PostgreSQL, specifically), or is it just syntax sugar for a CASE expression in an aggregate function? https://twitter.com/Ivan73965858/status/1622487080088600576 As a quick reminder, FILTER is an awesome standard SQL extension to filter out values before aggregating them in SQL. … Continue reading The Performance Impact of SQL’s FILTER Clause