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Chapter 14. Programming in SPL
This chapter first describes the basic elements of an SPL program. The chapter then provides an overview of the organization of an SPL program and how it is used to create a procedure or a function. Triggers, while still utilizing SPL, are sufficiently different to warrant a separate discussion. See Chapter 15. The remaining sections of the chapter delve into the details of the SPL language and provide examples of its application. 14.1. Basic SPL ElementsThis section discusses the basic programming elements of an SPL program. 14.1.1. Character SetSPL programs are written using the following set of characters:
Identifiers, expressions, statements, control structures, etc. that comprise the SPL language are written using these characters.
14.1.2. Case SensitivityKeywords and user-defined identifiers that are used in an SPL program are case insensitive. So for example, the statement DBMS_OUTPUT.PUT_LINE('Hello World'); is interpreted to mean the same thing as dbms_output.put_line('Hello World'); or Dbms_Output.Put_Line('Hello World'); or DBMS_output.Put_line('Hello World');. Character and string constants, however, are case sensitive as well as any data retrieved from the EnterpriseDB database or data obtained from other external sources. The statement DBMS_OUTPUT.PUT_LINE('Hello World!'); produces the following output: Hello World!
However the statement DBMS_OUTPUT.PUT_LINE('HELLO WORLD!'); produces the output: HELLO WORLD!
14.1.3. IdentifiersIdentifiers are user-defined names that are used to identify various elements of an SPL program including variables, cursors, labels, programs, and parameters. The syntax rules for valid identifiers are the same as for identifiers in the SQL language. See Section 3.1.1 for a discussion of SQL identifiers. An identifier must not be the same as an SPL keyword or a keyword of the SQL language. The following are some examples of valid identifiers: x last___name a_$_Sign Many$$$$$$$$signs_____ THIS_IS_AN_EXTREMELY_LONG_NAME A1
14.1.4. QualifiersA qualifier is a name that specifies the owner or context of an entity that is the object of the qualification. A qualified object is specified as the qualifier name followed by a dot with no intervening white space, followed by the name of the object being qualified with no intervening white space. This syntax is called dot notation. The following is the syntax of a qualified object. qualifier. [ qualifier. ]... objectqualifier is the name of the owner of the object. object is the name of the entity belonging to qualifier. It is possible to have a chain of qualifications, where the preceeding qualifier owns the entity identified by the subsequent qualifier(s) and object. Almost any identifier can be qualified. What an identifier is qualified by depends upon what the identifier represents and the context of its usage. Some examples of qualification follow:
As a general rule, wherever a name appears in the syntax of an SPL statement, its qualified name in dot notation can be used as well. Typically a qualified name would only be used if there is some ambiguity associated with the name. For example, if two procedures with the same name belonging to two different schemas are invoked from within a program or if the same name is used for a table column and SPL variable within the same program. It is suggested that qualified names be avoided if at all possible. In this chapter, the following conventions are adopted to avoid such naming conflicts:
14.1.5. ConstantsConstants or literals are fixed values that can be used in SPL programs to represent values of various types - e.g., numbers, strings, dates, etc. Constants come in the following types:
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