Cattle sql brush off network problems resolved - in the continually updated

Find all the information at the latest recruits

 

 

  Problem-solving steps:

　　　Title: query all the information at the latest recruits
  　     goal: All information query employee
　　　screening criteria: the latest entry
           answer:

. 1  the SELECT 
2      * - Search Information on the use of * 
. 3  the FROM 
. 4      the Employees
 . 5  the WHERE 
. 6      hire_date = ( - here a subquery, and hire_date as to match, so only one value, the max function usage rule attention 
. 7          the SELECT 
. 8              MAX (the hire_date)
 . 9          the FROM 
10              the Employees
 . 11      )

 

Find recruits ranked third time information of all employees

　　   

 

  Problem-solving steps:

　　　Topic: Finding recruits staff time ranked third all information
  　     Goal: All employees of the information inquiry
　　　filter criteria: the third entry time to
           answer:

. 1  the SELECT 
2      * - All information with * easy 
. 3  the FROM 
. 4      the Employees
 . 5  WHERE hire_date = ( the SELECT  the DISTINCT - subqueries noted hire_date is a value, a return value must be a subquery 
. 6                          hire_date
 . 7                      the FROM 
. 8                          the Employees
 . 9                      the ORDER  BY - there is a small tips, descending row, taken from the third, to a 
10                          the hire_date DESC 
. 11 limit 2 ,. 1 - page syntax take a closer look, limit m, n => take starts from m + 1, take the n 
12 )

 

Find all sectors of the current (to_date = '9999-01-01') leading the current salary details, and their corresponding department number dept_no

 

Problem-solving steps:

　　　Title: Find (to_date = '9999-01-01') leading the current salary details of the various departments and their counterparts in the current number dept_no
  　     target: query leadership salary details, the corresponding department number
　　　Filters: Department table of the current time, hidden conditions (salary table current time)
           answer:

1  the SELECT 
2      S. * ,
 3      d.dept_no
 4  the FROM 
5      salaries S - Leftist to the department table, salary table full of people, so the table is better to call the shots, the situation will not be associated with an empty 
6      LEFT  JOIN dept_manager d ON S .emp_no = d.emp_no
 . 7  the WHERE 
. 8      s.TO_DATE =  ' 9999-01-01 ' - filters 
. 9      the AND d.TO_DATE =  ' 9999-01-01 '