使用MySQL示例員工數據庫的SQL查詢

Question

我有一個問題，使高級（對我）查詢。

我想要得到管理員的名字，姓氏，頭銜，部門名稱以及姓名。如果由於某些原因你需要知道，我在PHP中使用這個SQL。我限制爲10個，因爲數據庫非常龐大。我只需要輸入員工最新的數據。他們有超過一個詞條，因爲工作促銷等。

我包括了一切，我認爲你需要了解我的問題。謝謝，如果你能幫助。

mysql> 
SELECT DISTINCT employees.first_name, employees.last_name, 
titles.title, departments.dept_name, z.first, z.last 
FROM employees, dept_emp, departments, titles, 
(
    SELECT employees.first_name AS first, employees.last_name AS last 
    FROM employees, dept_emp, dept_manager 
    WHERE 
     employees.emp_no = dept_emp.emp_no 
     AND dept_manager.emp_no = dept_emp.emp_no 
) AS z 
WHERE 
    employees.emp_no = dept_emp.emp_no 
    AND dept_emp.dept_no = departments.dept_no 
    AND titles.emp_no = employees.emp_no 
LIMIT 10; 

+------------+-----------+-----------------+-------------+-----------+--------------+ 
| first_name | last_name | title   | dept_name | first  | last   | 
+------------+-----------+-----------------+-------------+-----------+--------------+ 
| Georgi  | Facello | Senior Engineer | Development | Margareta | Markovitch | 
| Georgi  | Facello | Senior Engineer | Development | Vishwani | Minakawa  | 
| Georgi  | Facello | Senior Engineer | Development | Ebru  | Alpin  | 
| Georgi  | Facello | Senior Engineer | Development | Isamu  | Legleitner | 
| Georgi  | Facello | Senior Engineer | Development | Shirish | Ossenbruggen | 
| Georgi  | Facello | Senior Engineer | Development | Karsten | Sigstam  | 
| Georgi  | Facello | Senior Engineer | Development | Krassimir | Wegerle  | 
| Georgi  | Facello | Senior Engineer | Development | Rosine | Cools  | 
| Georgi  | Facello | Senior Engineer | Development | Shem  | Kieras  | 
| Georgi  | Facello | Senior Engineer | Development | Oscar  | Ghazalie  | 
+------------+-----------+-----------------+-------------+-----------+--------------+ 
10 rows in set (0.00 sec) 

數據庫是從mysql.com員工數據庫： http://dev.mysql.com/doc/index-other.html

mysql> desc departments; 
+-----------+-------------+------+-----+---------+-------+ 
| Field  | Type  | Null | Key | Default | Extra | 
+-----------+-------------+------+-----+---------+-------+ 
| dept_no | char(4)  | NO | PRI | NULL |  | 
| dept_name | varchar(40) | NO | UNI | NULL |  | 
+-----------+-------------+------+-----+---------+-------+ 
2 rows in set (0.22 sec) 

mysql> desc dept_emp; 
+-----------+---------+------+-----+---------+-------+ 
| Field  | Type | Null | Key | Default | Extra | 
+-----------+---------+------+-----+---------+-------+ 
| emp_no | int(11) | NO | PRI | NULL |  | 
| dept_no | char(4) | NO | PRI | NULL |  | 
| from_date | date | NO |  | NULL |  | 
| to_date | date | NO |  | NULL |  | 
+-----------+---------+------+-----+---------+-------+ 
4 rows in set (0.20 sec) 

mysql> desc dept_manager; 
+-----------+---------+------+-----+---------+-------+ 
| Field  | Type | Null | Key | Default | Extra | 
+-----------+---------+------+-----+---------+-------+ 
| dept_no | char(4) | NO | PRI | NULL |  | 
| emp_no | int(11) | NO | PRI | NULL |  | 
| from_date | date | NO |  | NULL |  | 
| to_date | date | NO |  | NULL |  | 
+-----------+---------+------+-----+---------+-------+ 
4 rows in set (0.21 sec) 

mysql> desc employees; 
+------------+---------------+------+-----+---------+-------+ 
| Field  | Type   | Null | Key | Default | Extra | 
+------------+---------------+------+-----+---------+-------+ 
| emp_no  | int(11)  | NO | PRI | NULL |  | 
| birth_date | date   | NO |  | NULL |  | 
| first_name | varchar(14) | NO |  | NULL |  | 
| last_name | varchar(16) | NO |  | NULL |  | 
| gender  | enum('M','F') | NO |  | NULL |  | 
| hire_date | date   | NO |  | NULL |  | 
+------------+---------------+------+-----+---------+-------+ 
6 rows in set (0.32 sec) 

mysql> desc salaries; 
+-----------+---------+------+-----+---------+-------+ 
| Field  | Type | Null | Key | Default | Extra | 
+-----------+---------+------+-----+---------+-------+ 
| emp_no | int(11) | NO | PRI | NULL |  | 
| salary | int(11) | NO |  | NULL |  | 
| from_date | date | NO | PRI | NULL |  | 
| to_date | date | NO |  | NULL |  | 
+-----------+---------+------+-----+---------+-------+ 
4 rows in set (0.34 sec) 

mysql> desc titles; 
+-----------+-------------+------+-----+---------+-------+ 
| Field  | Type  | Null | Key | Default | Extra | 
+-----------+-------------+------+-----+---------+-------+ 
| emp_no | int(11)  | NO | PRI | NULL |  | 
| title  | varchar(50) | NO | PRI | NULL |  | 
| from_date | date  | NO | PRI | NULL |  | 
| to_date | date  | YES |  | NULL |  | 
+-----------+-------------+------+-----+---------+-------+ 
4 rows in set (0.60 sec) 

Answer 1

我想獲得的第一個名字，姓氏，職務，部門名稱，第一個和最後經理姓名

使用該理論（但如果您有大型表格可能沒有優化），請一步步完成。假設你有一個包含日期的$date PHP變量（如date('Y-m-d 00:00:00')的結果），否則你可以使用MySQL的日期。

1 /讓員工的身份：

SELECT 
    e.first_name, 
    e.last_name 
FROM 
    employees AS e 
WHERE 
    1 

2 /添加他/她的當前標題

SELECT 
    e.first_name, 
    e.last_name, 
    t.title 
FROM 
    employees AS e, 
    titles AS t 
WHERE 
    e.emp_no=t.emp_no AND t.from_date<='$date' AND t.to_date>='$date' 

3 /讓他/她目前的部門（從dept_emp）和檢索部門名稱

SELECT 
    e.first_name, 
    e.last_name, t.title, 
    d.dept_name 
FROM 
    employees AS e, 
    titles AS t, 
    dept_emp AS de, 
    departments as d 
WHERE 
    e.emp_no=t.emp_no AND t.from_date<='$date' AND t.to_date>='$date' 
AND 
    e.emp_no=de.emp_no AND de.from_date<='$date' AND de.to_date>='$date' 
AND 
    d.dept_no=de.dept_no 

4 /得到部門的經理（從dept_manager）和重新trieve他/她的名字（從employees）

SELECT 
    e.first_name AS empFN, 
    e.last_name AS empLN, 
    t.title AS empT, 
    d.dept_name AS dept, 
    em.first_name AS manFN, 
    em.last_name AS manLN 
FROM 
    employees AS e, 
    titles AS t, 
    dept_emp AS de, 
    departments as d, 
    dept_manager AS dm, 
    employees AS em 
WHERE 
    e.emp_no=t.emp_no AND t.from_date<='$date' AND t.to_date>='$date' 
AND 
    e.emp_no=de.emp_no AND de.from_date<='$date' AND de.to_date>='$date' 
AND 
    d.dept_no=de.dept_no 
AND 
    em.emp_no=dm.emp_no AND dm.from_date<='$date' AND dm.to_date>='$date' 
AND 
    de.dept_no=dm.dept_no 

那裏，您可以追加一個LIMIT（和ORDER BY可能的是，你不知道哪個結果的情況下將採摘的限制），和/或添加WHERE和emp_no爲您想要了解有關信息的員工。雖然未經過測試，但主要是讓您瞭解如何構建請求。

這是理論，這個請求可能和你寫的一樣重。由於您在PHP中使用SQL，因此最好只檢索您感興趣的主鍵，然後發送簡短的請求以檢索所需的信息。喜歡的東西，我的意思是（使用假功能，但精神在這裏）：

$dateString="from_date<='$date' AND to_date>='$date'"; 
$qe=query("SELECT emp_no, first_name, last_name, dept_no FROM employees, dept_emp WHERE dept_emp.emp_no=employees.emp_no LIMIT 10 ORDER BY emp_no DESC"); 
while($r=fetch($qe)) { 
    $qt=fetch(query("SELECT title FROM titles WHERE emp_no=".$qe['emp_no']." AND ".$dateString)); 
    $qd=fetch(query("SELECT dept_name FROM departments WHERE dept_no=".$qe['dept_no']." AND ".$dateString)); 
    $qm=fetch(query("SELECT first_name, last_name FROM employees AS e, dept_manager AS dm WHERE dept_no=".$qe['dept_no']." AND e.emp_no=dm.emp_no AND ".$dateString)); 
    //echo/process here 
} 

希望這有助於:)