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mysql視圖之管理視圖實(shí)例詳解【增刪改查操作】

發(fā)布時(shí)間:2020-09-12 02:33:02 來(lái)源:腳本之家 閱讀:234 作者:luyaran 欄目:MySQL數(shù)據(jù)庫(kù)

本文實(shí)例講述了mysql視圖之管理視圖操作。分享給大家供大家參考,具體如下:

mysql提供了用于顯示視圖定義的SHOW CREATE VIEW語(yǔ)句,我們來(lái)看下語(yǔ)法結(jié)構(gòu):

SHOW CREATE VIEW [database_name].[view_ name];

要顯示視圖的定義,需要在SHOW CREATE VIEW子句之后指定視圖的名稱(chēng),我們先來(lái)根據(jù)employees表創(chuàng)建一個(gè)簡(jiǎn)單的視圖用來(lái)顯示公司組織結(jié)構(gòu),完事在進(jìn)行演示:

CREATE VIEW organization AS
  SELECT 
    CONCAT(E.lastname, E.firstname) AS Employee,
    CONCAT(M.lastname, M.firstname) AS Manager
  FROM
    employees AS E
      INNER JOIN
    employees AS M ON M.employeeNumber = E.ReportsTo
  ORDER BY Manager;

從以上視圖中查詢(xún)數(shù)據(jù),得到以下結(jié)果:

mysql> SELECT * FROM organization;
+------------------+------------------+
| Employee     | Manager     |
+------------------+------------------+
| BondurLoui    | BondurGerard   |
| CastilloPamela  | BondurGerard   |
| JonesBarry    | BondurGerard   |
| HernandezGerard | BondurGerard   |
.......此處省略了many many數(shù)據(jù).......
| KatoYoshimi   | NishiMami    |
| KingTom     | PattersonWilliam |
| MarshPeter    | PattersonWilliam |
| FixterAndy    | PattersonWilliam |
+------------------+------------------+
24 rows in set

要顯示視圖的定義,請(qǐng)使用SHOW CREATE VIEW語(yǔ)句如下:

SHOW CREATE VIEW organization;

我們還可以使用任何純文本編輯器(如記事本)顯示視圖的定義,以打開(kāi)數(shù)據(jù)庫(kù)文件夾中的視圖定義文件。例如,要打開(kāi)organization視圖定義,可以在數(shù)據(jù)庫(kù)文件夾下的data文件夾中找到你數(shù)據(jù)庫(kù)文件夾,完事進(jìn)入其中按著你視圖名稱(chēng)找.frm文件。

我們?cè)賮?lái)通過(guò)ALTER VIEW和CREATE OR REPLACE VIEW來(lái)嘗試修改視圖,先來(lái)看下alert view語(yǔ)法:

ALTER
 [ALGORITHM = {MERGE | TEMPTABLE | UNDEFINED}]
 VIEW [database_name]. [view_name]
  AS
 [SELECT statement]

以下語(yǔ)句通過(guò)添加email列來(lái)演示如何修改organization視圖:

ALTER VIEW organization
 AS 
 SELECT CONCAT(E.lastname,E.firstname) AS Employee,
     E.email AS employeeEmail,
     CONCAT(M.lastname,M.firstname) AS Manager
 FROM employees AS E
 INNER JOIN employees AS M
  ON M.employeeNumber = E.ReportsTo
 ORDER BY Manager;

要驗(yàn)證更改,可以從organization視圖中查詢(xún)數(shù)據(jù),咱就不贅述了,完事來(lái)看下另一個(gè)語(yǔ)法結(jié)構(gòu):

CREATE OR REPLACE VIEW v_contacts AS
  SELECT 
    firstName, lastName, extension, email
  FROM
    employees;
-- 查詢(xún)視圖數(shù)據(jù)
SELECT * FROM v_contacts;

我們要注意,在我們修改的時(shí)候,如果一個(gè)視圖已經(jīng)存在,mysql只會(huì)修改視圖。如果視圖不存在,mysql將創(chuàng)建一個(gè)新的視圖。好啦,我們來(lái)看下上述sql執(zhí)行的結(jié)果:

+-----------+-----------+-----------+--------------------------------+
| firstName | lastName | extension | email             |
+-----------+-----------+-----------+--------------------------------+
| Diane   | Murphy  | x5800   | dmurphy@yiibai.com       |
| Mary   | Hill   | x4611   | mary.hill@yiibai.com      |
| Jeff   | Firrelli | x9273   | jfirrelli@yiibai.com      |
| William  | Patterson | x4871   | wpatterson@yiibai.com     |
| Gerard  | Bondur  | x5408   | gbondur@gmail.com       |
| Anthony  | Bow    | x5428   | abow@gmail.com         |
| Leslie  | Jennings | x3291   | ljennings@yiibai.com      |
.............. 此處省略了many many數(shù)據(jù) ..................................
| Martin  | Gerard  | x2312   | mgerard@gmail.com       |
| Lily   | Bush   | x9111   | lilybush@yiiibai.com      |
| John   | Minsu   | x9112   | johnminsu@classicmodelcars.com |
+-----------+-----------+-----------+--------------------------------+
25 rows in set

假設(shè)我們要將職位(jobtitle)列添加到v_contacts視圖中,只需使用以下語(yǔ)句:

CREATE OR REPLACE VIEW v_contacts AS
  SELECT 
    firstName, lastName, extension, email, jobtitle
  FROM
    employees;
-- 查詢(xún)視圖數(shù)據(jù)
SELECT * FROM v_contacts;

執(zhí)行上面查詢(xún)語(yǔ)句后,可以看到添加一列數(shù)據(jù):

+-----------+-----------+-----------+--------------------------------+----------------------+
| firstName | lastName | extension | email             | jobtitle       |
+-----------+-----------+-----------+--------------------------------+----------------------+
| Diane   | Murphy  | x5800   | dmurphy@yiibai.com       | President      |
| Mary   | Hill   | x4611   | mary.hill@yiibai.com      | VP Sales       |
| Jeff   | Firrelli | x9273   | jfirrelli@yiibai.com      | VP Marketing     |
................... 此處省略了一大波數(shù)據(jù) ....................................................
| Yoshimi  | Kato   | x102   | ykato@gmail.com        | Sales Rep      |
| Martin  | Gerard  | x2312   | mgerard@gmail.com       | Sales Rep      |
| Lily   | Bush   | x9111   | lilybush@yiiibai.com      | IT Manager      |
| John   | Minsu   | x9112   | johnminsu@classicmodelcars.com | SVP Marketing    |
+-----------+-----------+-----------+--------------------------------+----------------------+
25 rows in set

完事我們來(lái)看使用DROP VIEW語(yǔ)句將視圖刪除,先來(lái)看下語(yǔ)法結(jié)構(gòu):

DROP VIEW [IF EXISTS] [database_name].[view_name]

上述sql中,IF EXISTS是語(yǔ)句的可選子句,它允許我們檢查視圖是否存在,用來(lái)避免刪除不存在的視圖的錯(cuò)誤。完事我們來(lái)刪除organization視圖:

DROP VIEW IF EXISTS organization;

我們得注意下,每次修改或刪除視圖時(shí),mysql會(huì)將視圖定義文件備份到/database_name/arc/目錄中。 如果我們意外修改或刪除視圖,可以從/database_name/arc/文件夾獲取其備份。

好啦,本次記錄就到這里了。

更多關(guān)于MySQL相關(guān)內(nèi)容感興趣的讀者可查看本站專(zhuān)題:《MySQL查詢(xún)技巧大全》、《MySQL事務(wù)操作技巧匯總》、《MySQL存儲(chǔ)過(guò)程技巧大全》、《MySQL數(shù)據(jù)庫(kù)鎖相關(guān)技巧匯總》及《MySQL常用函數(shù)大匯總》

希望本文所述對(duì)大家MySQL數(shù)據(jù)庫(kù)計(jì)有所幫助。

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