It is used to identify a value for a parameter name. Here's an example:
CREATE PROCEDURE my_proc (parm1 IN varchar2, parm2 IN date DEFAULT sysdate, parm3 IN number) AS . . . code for this procedure would go here. . .Now, when you want to call this procedure in a PL/SQL code block, you'd call it as follows:
begin my_proc('XYZ', to_date('12/12/2002','mm/dd/yyyy'), 123) ; end; /But, what if you wanted to call the procedure and not pass the second parameter (parm2 IN date) and simply allow it to use the default of sysdate which you specified in the procedure parameter definition. This is how you'd do it:
begin my_proc(parm1 => 'XYZ', parm3 => 123) ; end; /So... "=>" is used to assign the value indicated to the named parameter. You can use this syntax every time you call the procedure for clarity and to "self-document" your code as well.
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This was first published in December 2002