Oracle Certification - SQL Fundamentals I - WHERE Clause

The WHERE Clause

The WHERE clause allows the rows returned by the SELECT statement to be restricted, based on one or more conditions.

Conditional clauses in the exam tend to focus on syntactical errors, so pay close attention to quotations marks et cetera.

Numeric Conditions

Note that conditions with incorrect data-types are automatically cast, i.e.

Character Based Conditions

Character based conditions must be enclosed in single quotes:

Date Based Conditions

These mostly focus on the DD-MON-RR date format, i.e. for RR between 50-99 Oracle assumes he previous century.

LIKE

The like operator uses two wild-card characters, _ (underscore) for a single wild-card character, and the % (percent) for zero of more wild-card characters. There is also the possibility of using the ESCAPE identifier to specify a character that proceeds escaped characters.

Boolean Operators

AND. OR and NOT. They act exactly as you would expect. The distinction between boolean and conditional clauses is important for the exam.

There is going to close attention paid to all of these operators, both on their syntax and operation.

Next up is The ORDER BY Clause.