Cambridge O Level Computer Science · Syllabus 2210 · Databases
Structured Query Language
What is Structured Query Language?
The language used to query data held in a database; at Cambridge O Level 2210 a query is limited to SELECT, FROM, WHERE, ORDER BY ASCENDING or DESCENDING, SUM, COUNT, AND and OR, applied to a single table.
This definition is part of the Databases chapter in Cambridge O Level Computer Science.
Structured Query Language in context
Structured Query Language (SQL) is the language used to ask questions of a database. A Topic 9 query is built from at most four clauses, always written in the order SELECT, FROM, WHERE, ORDER BY, and finished with a semicolon. That written order is not the order the query is worked out in. The table is fetched first, the records are filtered next, the chosen fields are taken after that, any total or count is calculated, and the sort happens last. Getting those two orders straight is the single most useful thing in this half of the chapter.