迁移需求 xxx项目适配人大金仓，测试环境195pgsql数据库需要进行迁移至192.168.3.29 人大金仓数据库； 数据库信息 ip os登录账号密码 数据库类型 数据库端口 数据库 数据库用户密码 源库 192.168.3.195 root/top@123 PG14.2 5432 ahtjtestnew ahtjtest/123456 目标库 1

多表联查 内联查询 SELECT e.department_id, e.first_name, d.department_nameFROM employees eINNER JOIN departments d-- JOIN departments dON e.department_id = d.department_id; 左外联查询 SELECT e.depa

分组 SELECT hire_date, COUNT(*)FROM employeesGROUP BY hire_date; SELECT extract(year from hire_date), COUNT(*)FROM employeesGROUP BY extract(year from hire_date);-- GROUP BY 1; SELECT extr

分组 SELECT hire_date, COUNT(*)FROM employeesGROUP BY hire_date; SELECT extract(year from hire_date), COUNT(*)FROM employeesGROUP BY extract(year from hire_date);-- GROUP BY 1; SELECT extr