3.3 Formatting Control Structures

Chapter 3
Effective Coding Style

 

---

The control structures in your program are the most direct representation of the logic needed to implement your specifications. The format of these control structures, therefore, will have a significant impact on the readability of your code.

Indentation is the most important element of control structure layout. Always keep statements of the same "logical level" at the same indentation level. Let's see what this means for the various control structures of PL/SQL.

3.3.1 Formatting IF Statements

This conditional construct comes in three flavors:

IF <expression> END IF; 

IF <expression> ELSE END IF; 

IF <expression> ELSEIF <expression> ELSE END IF; 

In general, the IF statement is composed of clauses in which there is a Boolean expression or condition and a section of code executed when that condition evaluates to TRUE.

So if you want to use indentation to reveal the logical structure of the simplest form of the IF statement (IF-END IF), I suggest one of these two styles:

New Line for THEN	Same Line for THEN
IF <expression> THEN executable_statements; END IF;	IF <expression> THEN executable_statements END IF;
IF <expression> THEN executable_statements; ELSE else_executable_statements; END IF;	IF <expression> THEN executable_statements ELSE else_executable_statements; END IF;
IF <expression>1 THEN executable_statements1; ELSEIF <expression2> THEN executable_statements2; ... ELSEIF <expressionN> THEN executable_statementsN; ELSE else_executable_statements; END IF;	IF <expression>1 THEN executable_statements1; ELSEIF <expression2> THEN executable_statements2; ... ELSEIF <expressionN> THEN executable_statementsN; ELSE else_executable_statements; END IF;

Notice that in both versions the executable statements are indented three spaces from the column in which the IF and END IF reserved words are found. The only difference between the two formats is the placement of the THEN reserved word. I prefer the new line format, in which the THEN appears on a line by itself after the IF condition. This format provides more whitespace than the other. I could create the whitespace by using a blank, rather than indenting three spaces, but then the executable statements for the IF clause are made distinct from the condition -- and they are logically connected. Let's examine some actual code to get a better sense of the differences.

The following example shows proper IF statement indentation with THEN on the same line:

IF max_sales > 2000 THEN    notify_accounting ('over_limit');    RAISE FORM_TRIGGER_FAILURE; END IF;

This code has proper IF statement indentation with THEN on the next line:

IF max_sales > 2000 THEN    notify_accounting ('over_limit');    RAISE FORM_TRIGGER_FAILURE; END IF;