常用SQL

常用SQL：

1. 查看数据库连接数情况：

   select * from pg_stat_activity;

2. 查找表中重复记录,重复记录是根据单个字段来判断,并统计重复次数

   SELECT [重复字段],COUNT(1) AS num FROM [表名]GROUP BY [重复字段] HAVING COUNT(1) > 1