Padding PLSQL operators and keywords

One of the most important elements in creating readable code is the spacing placed around operators. Below shows common operators and keywords that need to be preceded and followed by a space when they are used in expressions.

Operators and keywords to be preceded and followed by a space in expressions

+ - * /
& < > =
!= <= >= :=
=> || .. :
<> IN OUT AND
OR NOT NULL

Often more than one of the operators and keywords shown in above table will be adjacent to each other inside an expression. In this instance, it is recommended that only one space lie between the two operators/identifiers. For example:

IF (vMajor IS NOT NULL) THEN

Reference: http://www.dba-oracle.com/t_plsql_coding_spacing_standards.htm