Oracle SQL: the Essential Reference

7.4. Execution Section

The execution section of a PL/SQL block is the only required section. It contains the PL/SQL code that actually performs some action; the exception section also performs an action, but only after being triggered by an action in the execution section. The general syntax of the execution section is:

BEGIN
   {assignment_statement    |
     proc_call    |
     control_statement    |
     PL/SQL_block    |
     SQL
				
				};
   [{assignment_statement    |
     proc_call    |
     control_statement    |
     PL/SQL_block    |
     SQL
    }; . . . ]
END;

7.4.1. Assignment Statements

An assignment statement provides a value to a PL/SQL variable. The general syntax of a PL/SQL assignment statement is:

					variable := expression;

Keywords

variable

Any previously declared PL/SQL variable.

:=

The PL/SQL symbol for assignment. Note the difference between := and the typical = used in many other languages.

expression

Any valid PL/SQL expression.

7.4.2. Expressions

PL/SQL expressions consist of one or more PL/SQL variables optionally combined with one or more PL/SQL operators. In PL/SQL, an expression may appear in one of the following locations:

• On the right side of an assignment statement

• As part of a control statement

• As part of a SQL statement

The PL/SQL operators that may be used in expressions, along with their relative precedence (where 1 is the highest) are listed in Table 7-4.

Table 7-4. PL/SQL Operators

Operator	Description	Type	Precedence
||	Concatenate two character strings	Character	4
+	Addition	Numeric	4
+	Unary identity ...