如何针对以下问题做出选择陈述？

问题描述

很抱歉提出一个简单的问题，但是您如何创建此Select语句以及您的思考过程是什么？ 我列出了我认为此选择语句所需的下表。

问题：创建SELECT语句以显示服务次数的列表 每个员工的要求。显示人员ID，人员名称，service_no，服务 说明和请求的总次数。

Table: SERVICES
Column Name || Constraints || Default Value || Data Type || Length
SERVICE_NO  || Primary Key ||               || VarChar2  || 10
DESCRIPTION ||             ||               || VarChar2  || 50
CONTRACTOR  ||             ||               || VarChar2  || 20
CCONTACT_NO ||             ||               || VarChar2  || 10

Table: SERVICE_REQUEST
Column Name  || Constraints                          || Default Value || Data Type || Length
SR_ID        || Primary Key                          ||               || Number    || 10
SERVICE_NO   || Foreign Key to the SERVICES table    ||               || VarChar2  || 10
STAFF_ID     || Foreign Key to the STAFF table       ||               || VarChar2  || 10
TEC_ID       || Foreign Key to the TECHNICIANS table ||               || VarChar2  || 10
REQUEST_DATE ||                                      ||               || Date      ||
REQUEST_TIME ||                                      ||               || VarChar2  || 10

Table: STAFF
Column Name || Constraints                       || Default Value || Data Type || Length
STAFF_ID    || Primary key                       ||               || VarChar2  || 10
SNAME       ||                                   ||               || VarChar2  || 30
SIC_NO      || Secondary key                     ||               || VarChar2  || 10
SADDRESS    ||                                   ||               || VarChar2  || 70
SPHONE      ||                                   ||               || VarChar2  || 8
POSITION    ||                                   ||               || VarChar2  || 30
HIRE_DATE   ||                                   ||               || Date      || 
SALARY      ||                                   ||               || Number    || 7,2
SCH_ID      || Foreign Key to the SCHOOL table   ||               || VarChar2  || 10

解决方法

使用查询。

select s.staff_id,s.sname,ser.service_no,ser.description,(select count(service_no) from staff where service_no = ser )
 from service_request sr,services ser
where  s.staff_id = sr.staff_id 
and ser.service_no = sr.service_no;