4 ms·

Getting rid of the 'IN' clause.

• Herald_MJ 16y ago
  exactly. Using an IN statement with a subquery is textbook "how to make a query slow" - it forces a sequential scan. No-one who understands SQL would write a query like that.
  • encoderer 16y ago
    It's certainly a cardinal sin on MySQL but commercial platforms have optimizations that make these correlated subqueries performant.
  • Lozzer 16y ago
    It's not inherent in SQL, it's down to the optimizer