SQL
Definition.
SQL: Structured Query Language, a domain-specific language used in programming and designed for managing data held in a relational database management system.
In More Detail
SQL is declarative: you describe the result you want and the query planner decides how to get it. That is why the same query can be fast on one dataset and slow on another — the plan changed, not the SQL.
Which makes `EXPLAIN` the tool worth learning first. A sequential scan over a large table where you expected an index lookup explains most 'the database is slow' reports, and the fix is usually a missing index or a query written so an existing index cannot be used.
In Practice
Even on Django projects where the ORM handles most queries, I still write and review the raw SQL for anything performance-sensitive — an ORM can hide an accidentally expensive query until it's running slowly in production.
Related Terms
Browse the full software development glossary, or see the frequently asked questions.
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