6.3. SQL Queries
We shall look at SQL’s query language to see how it relates to event specifications. But our ultimate interest isn’t in SQL itself, but in how the computer answers the queries.
An SQL query can combine information from several tables in almost any way imaginable. This means that the designer of the database schema is freed from considering the reports and forms that will display what is in the database and can focus on the logical relationships between the atoms it represents.
SQL was originally intended for non-programmers to be able to ask for information from complex databases. For that reason, it has a sophisticated syntax for expressing queries. The basic form of an SQL query is where {columnA, columnB, …} is a subset of ...
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