一个查询,该查询应给出具有年份的输出作为该年度雇用的雇员的列名和编号。聘用日期将是他们在列hire_date
。 我写了代码它像 SELECT count(e.employee_id) total, count(a.employee_id) _2002, count(b.employee_id) _2003, count(c.employee_id) _2004, count(d.employee_id) _2005
FROM hr.employees e, (select employee_id from hr.employees where extract(year from hire_date)=2002) a, (select employee_id from hr.employees where extract(year from hire_date)=2003) b, (select employee_id from hr.employees where extract(year from hire_date)=2004) c, (select employee_id from hr.employees where extract(year from hire_date)=2005) d;
。
它在每一列显示'0'。我哪里错了?from from子句的集合函数
注意:所有条件都存在数据。