Question 25

Explanation

True Statements:

1. If arg1 is VARCHAR2, then Oracle DB converts arg2 to the datatype of arg1 before comparing them and returns VARCHAR2 in the character set of arg1.

   1. Oracle performs implicit conversion of arg2 to match the datatype of arg1 when they differ.

   2. If arg1 is character data, arg2 is converted to that character type and the result is in the character set of arg1.

2. Explicit conversions are preferred to implicit conversions if arg1 is a different datatype than arg2.

   1. While Oracle allows implicit conversions, it is best practice to use explicit conversions to avoid unexpected behavior or errors.

   2. This ensures clarity and control over how data is interpreted and returned.

False Statements :

• "An NVL function cannot be used with arguments of DATE datatype"
  → Incorrect. NVL can be used with DATE values, as long as both arguments are of compatible types.

• "The arguments arg1 and arg2 must be matching data types."
  → Not strictly true. Oracle allows different datatypes and performs implicit conversion when necessary.

• "The two expressions arg1 and arg2 should only be in VARCHAR2 or NUMBER data type format."
  → False. NVL supports any datatype, including DATE, TIMESTAMP, and more, as long as they are compatible or convertible.

Implicit conversions are not visible to the user. SQL Server automatically converts the data from one data type to another. For example, when a smallint is compared to an int, the smallint is implicitly converted to int before the comparison proceeds. GETDATE() implicitly converts to date style 0. SYSDATETIME() implicitly converts to date style 21.

Explicit conversions use the CAST or CONVERT functions. The CAST and CONVERT functions convert a value (a local variable, a column, or another expression) from one data type to another. For example, the following CAST function converts the numeric value of $157.27 into a character string of '157.27':

NVL

NVL lets you replace null (returned as a blank) with a string in the results of a query. If expr1 is null, then NVL returns expr2. If expr1 is not null, then NVL returns expr1.

The arguments expr1 and expr2 can have any data type. If their data types are different, then Oracle Database implicitly converts one to the other. If they cannot be converted implicitly, then the database returns an error. The implicit conversion is implemented as follows:

If expr1 is character data, then Oracle Database converts expr2 to the data type of expr1 before comparing them and returns VARCHAR2 in the character set of expr1.

If expr1 is numeric, then Oracle Database determines which argument has the highest numeric precedence, implicitly converts the other argument to that data type, and returns that data type.

√  If arg1 is VARCHAR2, then Oracle DB converts arg2 to the datatype of arg1 before comparing them and returns VARCHAR2 in the character set of arg1.

Implicit conversions are never necessary. Explicit conversions are always simple. Always use the correct datatype. If you must convert from one datatype to another, use an explicit conversion.

√  Explicit conversions are preferred to implicit conversions if arg1 is a different datatype than arg2.

The Oracle/PLSQL NVL function lets you substitute a value when a null value is encountered.

Syntax

The syntax for the NVL function in Oracle/PLSQL is:

NVL( string1, replace_with )

Parameters or Arguments

string1 - The string to test for a null value.

replace_with - The value returned if string1 is null.

Returns

The NVL function returns a substitute value.

https://www.techonthenet.com/oracle/functions/nvl.php