9.5 Object Query Language (OQL)

OQL uses a syntax that is similar to SQL, but it operates on objects, not tables. One form for queries is

Line 1. SELECT open square bracket DISTINCT close square bracket expression hyphen list. Line 2. FROM from hyphen list. Line 3. Open square bracket WHERE condition close square bracket. Line 4. Open square bracket GROUP BY dot, dot, dot open square bracket HAVING condition close square bracket close square bracket. Line 5. Open square bracket ORDER BY expression close square bracket semicolon.

Although the syntax is similar to SQL, there are some important differences. The expression list may contain the names of attributes of objects, identified by using dot notation, as in

Line 1. SELECT s dot p I d comma s dot credits. Line 2. FROM Students s. Line 3. ORDER BY s dot p I d semicolon.

The use of dot notation invokes the default get() method for the attributes named in the SELECT line. The result will be the values of pId and credits for each of the Student instances in the Students extent.

In addition to attributes, ...

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