I stumbled upon an interesting question on Stack Overflow recently. A user wanted to query a table for a given predicate. If that predicate returns no rows, they wanted to run another query using a different predicate. Preferably in a single query. Challenge accepted! Canonical Idea: Use a Common Table Expression We're querying the Sakila … Continue reading How to Execute a SQL Query Only if Another SQL Query has no Results
Tag: Common Table Expression
PostgreSQL Syntax is a Mystery Only Exceeded by its Power
I just ran across this rather powerful PostgreSQL example statement from the manual. It reads Increment the sales count of the salesperson who manages the account for Acme Corporation, and record the whole updated row along with current time in a log table: WITH upd AS ( UPDATE employees SET sales_count = sales_count + 1 … Continue reading PostgreSQL Syntax is a Mystery Only Exceeded by its Power