SQL Functions v/s User-defined Functions

SQL functions are built-in Database functions and are available for use in various SQL statements.

For a SQL function call with an argument of a datatype other than the datatype expected by the SQL function, Oracle attempts to convert the argument to the expected datatype before performing the SQL function.

If you call a SQL function with a null argument, then the SQL function automatically returns null. The only SQL functions that do not necessarily follow this behavior are CONCAT, NVL, REPLACE, and REGEXP_REPLACE.


Use-defined functions are the functions that are written in PL/SQL or Java to provide functionality that is not available in SQL or SQL built-in functions. User-defined functions can appear in a SQL statement anywhere SQL functions can appear, that is, wherever an expression can occur.

To use a user function in a SQL expression, you must own or have EXECUTE privilege on the user function. To query a view defined with a user function, you must have SELECT privileges on the view. No separate EXECUTE privileges are needed to select from the view.

User-defined functions must be created as top-level functions or declared with a package specification before they can be named within a SQL statement.


And hence one should not confuse with SQL functions and User-defined functions.

Set Java PATH

PATH Environment Variable - Windows

You can run Java applications just fine without setting the PATH environment variable. Or, you can optionally set it as a convenience.

Set the PATH environment variable if you want to be able to conveniently run the executables from any directory without having to type the full path of the command. If you do not set the PATH variable, you need to specify the full path to the executable every time you run it, such as:

C:\Java\jdk1.8.0\bin\javac MyClass.java

The PATH environment variable is a series of directories separated by semicolons (;). Microsoft Windows looks for programs in the PATH directories in order, from left to right. You should have only one bin directory for the JDK in the path at a time (those following the first are ignored), so if one is already present, you can update that particular entry.

The following is an example of a PATH environment variable:

C:\Java\jdk1.8.0\bin;C:\Windows\System32\;C:\Windows\;C:\Windows\System32\Wbem

It is useful to set the PATH environment variable permanently so it will persist after rebooting. To make a permanent change to the PATH variable, use the System icon in the Control Panel. The precise procedure varies depending on the version of Windows:

Windows 7:

1. From the desktop, right click the Computer icon.
2. Choose Properties from the context menu.
3. Click the Advanced system settings link.
4. Click Environment Variables. In the section System Variables, find the PATH environment variable and select it. Click Edit.
5. In the Edit System Variable window, specify the value of the PATH environment variable. Click OK. Close all remaining windows by clicking OK.

 

Windows 10

1. From the desktop, right click the This PC icon.
2. Choose Properties from the context menu.
3. Click the Advanced system settings link.
4. Click Environment Variables. In the section System Variables, find the PATH environment variable and select it. Click Edit.
5. In the Edit environment variable window, click on New and specify the value of the PATH environment variable. Click OK. Close all remaining windows by clicking OK.