• Should domain name resolution be broken


    Original address: https://www.wjcms.net/archive… preface Domain name servers respond to DNS requests based on resource records. In DNS system, the most common resource record is Internet class record. Resource record is a 4-tuple containing the following fields: name, value, type and TTL. Where TTL is the lifetime of the record, which determines when the resource record […]

  • Oracle analysis functions first value, last value


    The first value and last value analysis functions can take out the first and last values in a group according to a specific grouping and sorting FIRST_VALUE { (expr) [ {RESPECT | IGNORE} NULLS ] | (expr [ {RESPECT | IGNORE} NULLS ]) } OVER (analytic_clause) Under test 10:48:07 [email protected]> SELECT EMPNO, 10:48:15 2 DEPTNO, […]