MySQL - SHOW FUNCTION STATUS 语句

• MySQL SHOW FUNCTION STATUS 语句
• LIKE 子句
• WHERE 子句

MySQL SHOW FUNCTION STATUS 语句

函数是一段有组织的、可重用的代码块，用于执行单个相关操作。函数为您的应用程序提供了更好的模块化和高度的代码重用。您可以使用 CREATE FUNCTION 语句创建存储函数。

MySQL SHOW FUNCTION STATUS 语句显示存储函数的功能。它提供以下信息:-

• 过程的名称。
• 创建过程的数据库。
• 过程的类型。
• 过程的创建者。
• 修改日期等。

语法

以下是 SHOW FUNCTION STATUS 语句的语法:-

SHOW FUNCTION STATUS
   [LIKE 'pattern' | WHERE expr]

示例

以下语句显示存储函数的特性 -

SHOW FUNCTION STATUS\G;

输出

上述查询生成如下所示的输出 -

************** 1. row **************
                  Db: test
                Name: areaOfCircle
                Type: FUNCTION
             Definer: root@localhost
            Modified: -------------------
             Created: -------------------
       Security_type: DEFINER
             Comment:
character_set_client: cp850
collation_connection: cp850_general_ci
  Database Collation: utf8mb4_0900_ai_ci
************** 2. row **************
                  Db: test
                Name: demo
                Type: FUNCTION
             Definer: root@localhost
            Modified: -------------------
             Created: -------------------
       Security_type: DEFINER
             Comment:
character_set_client: cp850
collation_connection: cp850_general_ci
  Database Collation: utf8mb4_0900_ai_ci
************** 3. row **************
                  Db: test
                Name: sample
                Type: FUNCTION
             Definer: root@localhost
            Modified: -------------------
             Created: -------------------
       Security_type: DEFINER
             Comment:
character_set_client: cp850
collation_connection: cp850_general_ci
  Database Collation: utf8mb4_0900_ai_ci
************** 4. row **************
                  Db: test
                Name: while_example
                Type: FUNCTION
             Definer: root@localhost
            Modified: -------------------
             Created: -------------------
       Security_type: DEFINER
             Comment:
character_set_client: cp850
collation_connection: cp850_general_ci
  Database Collation: utf8mb4_0900_ai_ci
************** 5. row **************
                  Db: test
                Name: test
                Type: FUNCTION
             Definer: root@localhost
            Modified: -------------------
             Created: -------------------
       Security_type: DEFINER
             Comment:
character_set_client: cp850
collation_connection: cp850_general_ci
  Database Collation: utf8mb4_0900_ai_ci
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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LIKE 子句

使用 LIKE 子句，您可以指定一个模式来检索有关函数的信息。

示例

假设我们创建了一个新数据库，并使用 CREATE 语句在其中创建了 3 个函数，如下所示 -

CREATE demo;
use dem;
database changed
DELIMITER //
CREATE FUNCTION TestAdd(a INT, b INT) RETURNS INT DETERMINISTIC
   BEGIN
      DECLARE res INT;
      SET res=a+b;
      RETURN res;
   END//
   Query OK, 0 rows affected (0.29 sec)
CREATE FUNCTION TestSub (a INT, b INT) RETURNS INT DETERMINISTIC
   BEGIN
      DECLARE res INT;
      SET res=a-b;
      RETURN res;
   END//
   Query OK, 0 rows affected (0.29 sec)
CREATE FUNCTION TestMul (a INT, b INT) RETURNS INT DETERMINISTIC
   BEGIN
      DECLARE res INT;
      SET res=a*b;
      RETURN res;
   END//
   Query OK, 0 rows affected (0.29 sec)
CREATE FUNCTION TestDiv (a INT, b INT) RETURNS INT DETERMINISTIC
   BEGIN
      DECLARE res INT;
      SET res=a/b;
      RETURN res;
   END//
   Query OK, 0 rows affected (0.29 sec)
DELIMITER ;

以下查询检索有关名称以单词"Test"开头的过程的信息。

SHOW FUNCTION STATUS LIKE 'Test%'\G;

输出

查询执行后，将产生以下输出 -

************** 1. row **************
                  Db: demo
			    Name: TestAdd
			    Type: FUNCTION
		     Definer: root@localhost
		    Modified: 2021-05-14 06:37:04
		     Created: 2021-05-14 06:37:04
       Security_type: DEFINER
		     Comment: 
character_set_client: cp850
collation_connection: cp850_general_ci
  Database Collation: utf8mb4_0900_ai_ci
************** 2. row **************
                  Db: demo
			    Name: TestDiv
			    Type: FUNCTION
		     Definer: root@localhost
		    Modified: 2021-05-14 06:37:22
		     Created: 2021-05-14 06:37:22
       Security_type: DEFINER
		     Comment: 
character_set_client: cp850
collation_connection: cp850_general_ci
  Database Collation: utf8mb4_0900_ai_ci
************** 3. row **************
                  Db: demo
			    Name: TestMul
			    Type: FUNCTION
		     Definer: root@localhost
		    Modified: 2021-05-14 06:37:16
		     Created: 2021-05-14 06:37:16
       Security_type: DEFINER
		     Comment: 
character_set_client: cp850
collation_connection: cp850_general_ci
  Database Collation: utf8mb4_0900_ai_ci
************** 4. row **************
                  Db: demo
			    Name: TestSub
			    Type: FUNCTION
		     Definer: root@localhost
		    Modified: 2021-05-14 06:37:10
		     Created: 2021-05-14 06:37:10
       Security_type: DEFINER
		     Comment: 
character_set_client: cp850
collation_connection: cp850_general_ci
  Database Collation: utf8mb4_0900_ai_ci

WHERE 子句

您可以使用 SHOW PROCEDURE STATUS 语句的 WHERE 子句来检索符合指定条件的过程信息。

示例

假设我们使用 CREATE 语句在数据库中创建了一个名为 Emp 的表，如下所示 -

CREATE TABLE Emp(Name VARCHAR(255), DOB DATE, Location VARCHAR(255));

现在，我们使用 INSERT 语句向 Emp 表中插入一些记录 -

INSERT INTO Emp VALUES
('Amit', DATE('1970-01-08'), 'Hyderabad'),
('Sumith', DATE('1990-11-02'), 'Vishakhapatnam'),
('Sudha', DATE('1980-11-06'), 'Vijayawada');

假设我们创建了一个 getDob() 函数，它接受员工姓名作为参数，检索并返回 DOB 列的值。

DELIMITER //
CREATE FUNCTION test.getDob(emp_name VARCHAR(50))
   RETURNS DATE
   DETERMINISTIC
   BEGIN
      declare dateOfBirth DATE;
      select DOB into dateOfBirth from test.emp where Name = emp_name;
      return dateOfBirth;
   END//
DELIMITER ;

如果我们以同样的方式创建了如下所示的另一个表 -

CREATE TABLE student (Name VARCHAR(100), Math INT, English INT,
Science INT, History INT);

让我们在 student 表中插入一些记录 -

INSERT INTO student values
('Raman', 95, 89, 85, 81),
('Rahul' , 90, 87, 86, 81),
('Mohit', 90, 85, 86, 81),
('Saurabh', NULL, NULL, NULL, NULL );

以下函数更新上面创建的表 -

Create Function test.tbl_Update(S_name Varchar(50), M1 INT, 
M2 INT, M3 INT, M4 INT)
   RETURNS INT
   DETERMINISTIC
   BEGIN
      UPDATE student SET Math = M1, English = M2, Science = M3, 
	  History = M4 WHERE Name = S_name;
      RETURN 1;
   END //
DELIMITER ;

您可以使用 SHOW FUNCTION STATUS 语句验证数据库中的函数列表，如下所示 -

SHOW FUNCTION STATUS WHERE db = 'test'\G;

输出

上述查询产生以下输出 -

************** 1. row **************
                     Db: test
				   Name: getDob
				   Type: FUNCTION
				Definer: root@localhost
			   Modified: 2021-03-21 11:21:12
				Created: 2021-03-13 14:45:36
		  Security_type: DEFINER
				Comment: This is a sample comment
   character_set_client: cp850
   collation_connection: cp850_general_ci
	 Database Collation: utf8mb4_0900_ai_ci
************** 2. row **************
                     Db: test
				   Name: tbl_Update
				   Type: FUNCTION
				Definer: root@localhost
			   Modified: 2021-03-13 22:16:05
				Created: 2021-03-13 22:16:05
		  Security_type: DEFINER
				Comment: 
   character_set_client: cp850
   collation_connection: cp850_general_ci
	 Database Collation: utf8mb4_0900_ai_ci

以下查询将删除/丢弃上面创建的函数 -

DROP FUNCTION getDob;

DROP FUNCTION tbl_update;

由于我们已经删除了这两个函数。如果您再次验证函数列表，您将得到一个空集 -

SHOW FUNCTION STATUS WHERE db = 'test';
Empty set (0.00 sec)