The Java EE 7 Tutorial
This section briefly describes the syntax of the query language so that you can quickly move on to Example Queries. When you are ready to learn about the syntax in more detail, see Full Query Language Syntax.
39.3.1 Select Statements
A select query has six clauses:
ORDER BY. The
FROM clauses are required, but the
ORDER BY clauses are optional. Here is the high-level BNF syntax of a query language select query:
QL_statement ::= select_clause from_clause [where_clause][groupby_clause][having_clause][orderby_clause]
The BNF syntax defines the following clauses.
FROMclause defines the scope of the query by declaring one or more identification variables, which can be referenced in the
WHEREclauses. An identification variable represents one of the following elements:
Update and delete statements provide bulk operations over sets of entities. These statements have the following syntax:
update_statement :: = update_clause [where_clause] delete_statement :: = delete_clause [where_clause]
The update and delete clauses determine the type of the entities to be updated or deleted. The
WHERE clause may be used to restrict the scope of the update or delete operation.