departments 部門表
--dept_emp 部門員工表
--dept_manager 部門主管表
--employees 雇員表
--salaries 薪水表
--titile 職稱表
--* 查詢統計公司員工數量、男員工數量、女員工數量
select
count(employees.emp_no) from
employees;
select
count(employees.emp_no) from employees where gender ='m
';select
count(employees.emp_no) from employees where gender ='f
'; --
* 查詢員工最新薪水 (分頁，第一頁，每頁50行)
--select * from student limit ((當前頁數 - 1) * 每頁行數), 行數
select
*from salaries where to_date =
'9999-01-01
' limit 0,50;
--* 查詢部門列表需顯示當前主管名字
select departments.dept_no as
'部門編號
',departments.dept_name as
'部門名稱
',employees.first_name as'名字
',employees.last_name as'姓氏
'from departments,employees,dept_manager where departments.dept_no = dept_manager.dept_no and employees.emp_no = dept_manager.emp_no and dept_manager.to_date =
'9999-01-01';
--* 查詢 lillian haddadi的詳細資訊，及薪水調薪記錄 以及擔任某部門主管的詳細資訊
select
*from employees where employees.first_name =
'lillian
'and employees.last_name =
'haddadi';
--下面的語句為啥會卡死程式？
--因為有一張不必要查詢的表，相當於做了交叉鏈結查詢，會查詢到巨大乘積的資料，把from後面的salaries去掉就能查到了
--即使修改正確以後，上下兩句的效率也相差很多，下面的查詢語句明顯執行得慢很多
select salaries.emp_no,salaries.from_date,salaries.to_date,salaries.salary from salaries,employees where employees.first_name =
'lillian
'and employees.last_name =
'haddadi
'and employees.emp_no =
salaries.emp_no;
select salaries.emp_no,salaries.from_date,salaries.to_date,salaries.salary from salaries where salaries.emp_no in (select employees.emp_no from employees where employees.first_name =
'lillian
'and employees.last_name =
'haddadi');
--沒有找到擔任主管的資訊？可能是找職稱？
select
*from titles where titles.emp_no =
10019
;select
*from dept_manager,employees where employees.first_name =
'lillian
'and employees.last_name =
'haddadi
'and employees.emp_no =
dept_manager.emp_no; --
* 查詢 shahaf famili的詳細資訊，及薪水調薪記錄 以及擔任某部門主管的詳細資訊
select
*from employees where employees.first_name =
'shahaf
'and employees.last_name =
'famili';
select salaries.emp_no,salaries.from_date,salaries.to_date,salaries.salary from salaries,employees where employees.first_name =
'shahaf
'and employees.last_name =
'famili
'and employees.emp_no =
salaries.emp_no;
select
*from dept_manager,employees where employees.first_name =
'shahaf
'and employees.last_name =
'famili
'and employees.emp_no = dept_manager.emp_no;
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