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.
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 […]
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 […]
What is wrong with the above statement? The Answer: It is not legitimate to specify a length for LOB data types ( CLOB, BLOB, and BFILE) Instead, you should have used something like this Same is true about CLOB, BLOB, NCLOB and BFILE data types
ALIAS cannot be used within WHERE clause. It produces an error like this. Just remember it, because it 100% guaranteed situation on your exam. Even, if you remove double quotes from your ALIAS, the result still the same – it won’t work. An alias can be used in a query select […]