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.
select customer_id from orders group by customer_id having count(*) > 4; Question: What will be the result of executing the above query? Answer: It will return all rows where COUNT(*) > 4 even though COUNT(*) is not part of the SELECT list. As we know, whatever you want to […]
Can LONG columns be used in queries joined by set operators? The UNION, INTERSECT, and MINUS operators are not valid on LONG columns, but they can be used with UNION ALL
NVL function requires data type match. If you try to evaluate NUMBER data with NVL, then replacement value should also be NUMBER. It can’t be CHAR or VARCHAR2 for instance. select from NVL(order_total, 0) from orders; Statement above is perfectly fine because order_total column is NUMBER and replacement value 0 […]
SUBSTR will always return NULL if number of characters to retrieve was specified as negative SUBSTR will also return NULL if number of characters to retrieve was specified as zero