The sequence keywords CURVAL and NEXTVAL can’t be used in: the condition of a CHECK constraint the DEFAULT value of a table column the WHERE clause of a SELECT statement    

It may look strange from the first glance, but it will work actually. Subquery will produce a single value – the SUM of all salaries. The query will execute successfully and return the FIRST_NAME and LAST_NAME column values of every row in EMPLOYEES table. Each row will have a third […]

It is an interesting example that deserves to be considered since it is a guaranteed case on your exam. Let’s consider a typical INSERT statement where everything is right and the value being inserted fits column precision and scale  So, Precision is the total number of digits and Scale is the number […]

You can’t apply a TO_CHAR() function to an argument with CHAR data type because 10-JAN-16 is already a CHAR literal.  It will generate an error   You can’t apply a TO_DATE() function to an argument with DATE data type because  date_of_birth is already a DATE. It will generate an  error   But, […]

This is Oracle 12c feature. Prior to 12c, the DEFAULT for a column would not be applied if you explicitly (or implicitly) inserted a NULL into that column.  The NULL would override the DEFAULT value  — the DEFAULT would not get applied. Let’s have a look how Oracle would behave in 11.2.3 […]

When you encounter an ORA-01719 error, the following error message will appear: ORA-01719: outer join operator (+) not allowed in operand of OR or IN You tried to perform an outer join when using an OR condition or IN operator. It is not allowed when using outer joins. Let’s consider an example below […]

you can’t specify NULL for exp1 in NULLIF function select NULLIF(NULL, NULL) from dual; It will produce an error. (see below) But you can specify NULL for exp2, it will work select NULLIF(1, NULL) from dual;  

TIMESTAMP WITH TIME ZONE contains all of the values of TIMESTAMP as well as time zone displacement value. Data is normalized to the database time zone when it is stored in the database. When the data is retrieved, users see the data in the time zone applicable to their session.

Time. Candidates often either run out of time before finishing every question or have to rush to answer later questions. Time management and being able to read SQL quickly is key for this exam;

NUMBER is a numeric data type that can optionally have a precision and scale specified at creation. The precision can range from 1 to 38 and the scale from -84 to 127.