POSTGRESQL没有IFNULL函数,有 COALESCE COALESCE(value [, ...])The COALESCE function returns the first of its arguments that is not null. Null is returned only if all arguments are null. It is often used to substitute a default value for null values when data is retrieved for display, for example: SELECT COALESCE(description, short_description, '(none)') ... Like a CASE expression, COALESCE only evaluates the arguments that are needed to determine the result; that is, arguments to the right of the first non-null argument are not evaluated. This SQL-standard function provides capabilities similar to NVL and IFNULL, which are used in some other database systems. 没有DateDiff对应的函数,直接相减 date '2001-10-01' - date '2001-09-28' integer '3' (days)
DATEDIFF(date1,date2)date1 和 date2 参数是合法的日期或日期/时间表达式。
date2 - date1 结果就是天。
COALESCE
COALESCE(value [, ...])The COALESCE function returns the first of its arguments that is not null. Null is returned only if all arguments are null. It is often used to substitute a default value for null values when data is retrieved for display, for example: SELECT COALESCE(description, short_description, '(none)') ...
Like a CASE expression, COALESCE only evaluates the arguments that are needed to determine the result; that is, arguments to the right of the first non-null argument are not evaluated. This SQL-standard function provides capabilities similar to NVL and IFNULL, which are used in some other database systems. 没有DateDiff对应的函数,直接相减
date '2001-10-01' - date '2001-09-28' integer '3' (days)