Oracle PL/SQL Programming: A Developer's Workbook

Expert

20-21.	How should the format mask be changed in this call to TO_CHAR so that all extra spaces and padded zeros are removed? TO_CHAR (SYSDATE, 'Month DD, YYYY')
20-22.	What format mask element could you use to validate a date (i.e., raise an exception if a date uses a four-digit year)?
20-23.	The built-in TO_DATE function—just like the underlying database itself—can understand only one date format: either the default for the database instance or the “override” format provided in the call to TO_DATE. For example, if the default date mask is MM/DD/YYYY, these calls to TO_DATE work fine: TO_DATE ('1/7/1999') TO_DATE ('01-07-1999') TO_DATE ('Jan-19-99', 'MON-DD-RR') But these calls to TO_DATE raise errors: TO_DATE ('Jan-19-99') TO_DATE ('1999-1-1') Write a replacement smarter version of TO_DATE; the function should accept a single string argument and, if it represents a supported date format, return a date. Your function should support (at minimum) the following date formats: MM/DD M/DD/YY MM/DD/YYYY DD-MON MON DD, YYYY MONTH DD, YYYY DD-MON-YY DD-MON-YYYY MON-DD-YYYY
20-24.	Assume that the following data is in a table called a_bunch_of_numbers: number_col1 number_col2 1 99 2 98 3 97 ... ... 100 0 Write a query to retrieve rows where the difference between the two columns is less than or equal to 25.
20-25.	Professor Twoplus Two needs a function to generate a specific set of numbers for his experiments. He has identified this requirement: Given a number of length n, return a set of numbers with the last ...