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  We had discussed about the Date/Time data types in the chapter   Data Types . Now, let us see the Date/Time operators and Functions. The following table lists the behaviors of the basic arithmetic operators − The following is the list of all important Date and Time related functions available. AGE(timestamp, timestamp), AGE(timestamp) Example of the function AGE(timestamp, timestamp) is − testdb =# SELECT AGE ( timestamp '2001-04-10' , timestamp '1957-06-13' ); The above given PostgreSQL statement will produce the following result − age ------------------------- 43 years 9 mons 27 days Example of the function AGE(timestamp) is − testdb =# select age ( timestamp '1957-06-13' ); The above given PostgreSQL statement will produce the following result − age -------------------------- 55 years 10 mons 22 days CURRENT DATE/TIME() PostgreSQL provides a number of functions that return values related to the current date and time. Foll

PostgreSQL string functions are used primarily for string manipulation. The following table details the important string functions − ASCII(str) Returns the numeric value of the leftmost character of the string str. Returns 0 if str is an empty string. Returns NULL if str is NULL. ASCII() works for characters with numeric values from 0 to 255. testdb=# SELECT ASCII('2'); +---------------------------------------------------------+ | ASCII('2') | +---------------------------------------------------------+ | 50 | +---------------------------------------------------------+ 1 row in set (0.00 sec) testdb=# SELECT ASCII('dx'); +---------------------------------------------------------+ | ASCII('dx') | +---------------------------------------------------------+ | 100 |

  PostgreSQL numeric functions are used primarily for numeric manipulation and/or mathematical calculations. The following table details the numeric functions − ABS(X) The ABS() function returns the absolute value of X. Consider the following example − testdb =# SELECT ABS ( 2 ); +---------------------------------------------------------+ | ABS ( 2 ) | +---------------------------------------------------------+ | 2 | +---------------------------------------------------------+ 1 row in set ( 0.00 sec ) testdb =# SELECT ABS (- 2 ); +---------------------------------------------------------+ | ABS ( 2 ) | +---------------------------------------------------------+ | 2 | +---------------------------------------------------------+ 1 row in set ( 0.00 sec )