MySQL - RESIGNAL 语句



在使用 MySQL 中的存储过程时,管理其执行过程中可能出现的异常非常重要。否则,这些异常可能会导致过程突然终止。

为了解决此问题,MySQL 提供了一种通过错误处理程序处理异常的方法。这些处理程序可以使用 DECLARE ... HANDLER 语句声明。

MySQL RESIGNAL 语句

MySQL RESIGNAL 语句用于在存储过程中发生异常时向处理程序、应用程序或客户端提供错误信息。

RESIGNAL 特别用于错误处理程序中,并且必须始终包含属性。这些属性指定与引发的错误关联的 SQL 状态、错误代码和错误消息。

自定义错误消息

RESIGNAL 语句允许您使用 SET MESSAGE_TEXT 命令自定义错误消息,从而确保更流畅的过程执行。

语法

以下是 MySQL RESIGNAL 语句的语法:

RESIGNAL condition_value [SET signal_information_item]

其中,

  • condition_value 表示要返回的错误值,可以是“sqlstate_value”或“condition_name”。

  • signal_information_item 允许您设置与错误条件相关的其他信息。您可以指定各种信号信息项,例如 CLASS_ORIGIN、SUBCLASS_ORIGIN、MESSAGE_TEXT、MYSQL_ERRNO、CONSTRAINT_CATALOG、CONSTRAINT_SCHEMA、CONSTRAINT_NAME、CATALOG_NAME、SCHEMA_NAME、TABLE_NAME、COLUMN_NAME 或 CURSOR_NAME。

示例

在此示例中,我们创建一个过程,该过程接受学位的简写形式并返回其全称。如果我们提供无效的学位,即除 BBA、BCA、MD 和 ITI 之外的值,则使用 RESIGNAL 语句生成错误消息:

DELIMITER //
CREATE PROCEDURE example(IN degree VARCHAR(20), OUT full_form VARCHAR(50))
BEGIN
DECLARE wrong_choice CONDITION FOR SQLSTATE '45000';
DECLARE EXIT HANDLER FOR wrong_choice
RESIGNAL SET MESSAGE_TEXT = 'Given degree is not valid', MYSQL_ERRNO = 1001;
IF degree='BBA' THEN SET full_form = 'Bachelor of Business Administration'; 
ELSEIF degree='BCA' THEN SET full_form = 'Bachelor of Computer Applications'; 
ELSEIF degree='MD' THEN SET full_form = 'Doctor of Medicine';
ELSEIF degree='ITI' THEN SET full_form = 'Industrial Training Institute';
ELSE 
SIGNAL wrong_choice;
END IF;
END //
DELIMITER ;

您可以调用上述过程以检索结果,如下所示:

CALL example('MD', @fullform);

您可以使用以下 SELECT 语句检索变量的值:

SELECT @fullform;

获得的输出如下:

@fullform
医学博士

如果将无效值传递给过程,它将生成如下错误消息:

CALL example ('IIT', @fullform);

获得的输出如下:

ERROR 1001 (45000): Given degree is not valid

使用 RESIGNAL 处理警告

让我们再看一个示例,在该示例中,我们不向 RESIGNAL 语句传递可选属性:

DELIMITER // CREATE PROCEDURE testexample (num INT) BEGIN DECLARE testCondition1 CONDITION FOR SQLSTATE '01000'; DECLARE EXIT HANDLER FOR testCondition1 RESIGNAL; IF num < 0 THEN SIGNAL testCondition1; END IF; END // DELIMITER ;

您可以通过传递两个值来调用上述过程。但是,任何以“01”开头的 SQLSTATE 值都表示警告,因此查询将发出警告执行,如下所示:

CALL testexample(-15);

获得的输出如下:

Query OK, 0 rows affected, 1 warning (0.00 sec)

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使用客户端程序重新发出信号语句

我们还可以使用客户端程序执行重新发出信号。

语法

要通过 PHP 程序执行 resignal 语句,我们需要使用 mysqli 函数 query() 执行“存储过程”,如下所示:

$sql = "CREATE PROCEDURE example_new1(IN degree VARCHAR(20), OUT full_form Varchar(50)) BEGIN IF degree='B-Tech' THEN SET full_form = 'Bachelor of Technology'; ELSEIF degree='M-Tech' THEN SET full_form = 'Master of Technology'; ELSEIF degree='BSC' THEN SET full_form = 'Bachelor of Science'; ELSEIF degree='MSC' THEN SET full_form = 'Master of Science'; ELSE RESIGNAL SQLSTATE '01000' SET MESSAGE_TEXT = 'Choose from the existing values', MYSQL_ERRNO = 12121; RESIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'Given degree is not valid', MYSQL_ERRNO = 1001; END IF; END"; $mysqli->query($sql);

要通过 JavaScript 程序执行 resignal 语句,我们需要使用 mysql2 库的 query() 函数执行“存储过程”,如下所示:

var createProcedureSql = ` CREATE PROCEDURE example(IN degree VARCHAR(20), OUT full_form Varchar(50)) BEGIN IF degree='B-Tech' THEN SET full_form = 'Bachelor of Technology'; ELSEIF degree='M-Tech' THEN SET full_form = 'Master of Technology'; ELSEIF degree='BSC' THEN SET full_form = 'Bachelor of Science'; ELSEIF degree='MSC' THEN SET full_form = 'Master of Science'; ELSE RESIGNAL SQLSTATE '01000' -- Raise a warning SET MESSAGE_TEXT = 'Choose from the existing values', MYSQL_ERRNO = 12121; RESIGNAL SQLSTATE '45000' -- Raise an error SET MESSAGE_TEXT = 'Given degree is not valid', MYSQL_ERRNO = 1001; END IF; END`; con.query(createProcedureSql);

要通过 Java 程序执行 resignal 语句,我们需要使用 JDBC 函数 execute() 执行“存储过程”,如下所示:

String sql = "CREATE PROCEDURE example(IN degree VARCHAR(20), OUT full_form Varchar(50)) BEGIN IF degree='B-Tech' THEN SET full_form = 'Bachelor of Technology'; ELSEIF degree='M-Tech' THEN SET full_form = 'Master of Technology'; ELSEIF degree='BSC' THEN SET full_form = 'Bachelor of Science'; ELSEIF degree='MSC' THEN SET full_form = 'Master of Science'; ELSE RESIGNAL SQLSTATE '01000' SET MESSAGE_TEXT = 'Choose from the existing values', MYSQL_ERRNO = 12121; RESIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'Given degree is not valid', MYSQL_ERRNO = 1001; END IF; END"; statement.execute(sql);

要通过 Python 程序执行 resignal 语句,我们需要使用 **MySQL Connector/Python** 的 **execute()** 函数执行“存储过程”,如下所示:

resignal_statement = 'CREATE PROCEDURE example(IN degree VARCHAR(20), OUT full_form VARCHAR(50)) BEGIN IF degree='B-Tech' THEN SET full_form = 'Bachelor of Technology'; ELSEIF degree='M-Tech' THEN SET full_form = 'Master of Technology'; ELSEIF degree='BSC' THEN SET full_form = 'Bachelor of Science'; ELSEIF degree='MSC' THEN SET full_form = 'Master of Science'; ELSE RESIGNAL SQLSTATE '01000' SET MESSAGE_TEXT = 'Choose from the existing values', MYSQL_ERRNO = 12121; RESIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'Given degree is not valid', MYSQL_ERRNO = 1001; END IF; END;' cursorObj.execute(resignal_statement)

示例

以下是程序示例:

$dbhost = 'localhost'; $dbuser = 'root'; $dbpass = 'password'; $db = 'TUTORIALS'; $mysqli = new mysqli($dbhost, $dbuser, $dbpass, $db); if ($mysqli->connect_errno) { printf("Connect failed: %s", $mysqli->connect_error); exit(); } //printf('Connected successfully.'); //lets generate error messege using RESIGNAL statement $sql = " CREATE PROCEDURE example_new1(IN degree VARCHAR(20), OUT full_form Varchar(50)) BEGIN IF degree='B-Tech' THEN SET full_form = 'Bachelor of Technology'; ELSEIF degree='M-Tech' THEN SET full_form = 'Master of Technology'; ELSEIF degree='BSC' THEN SET full_form = 'Bachelor of Science'; ELSEIF degree='MSC' THEN SET full_form = 'Master of Science'; ELSE RESIGNAL SQLSTATE '01000' SET MESSAGE_TEXT = 'Choose from the existing values', MYSQL_ERRNO = 12121; RESIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'Given degree is not valid', MYSQL_ERRNO = 1001; END IF; END"; if($mysqli->query($sql)){ printf("Resignal statement created successfully....!\n"); } //lets call the above procedure $sql = "CALL example_new('BSC', @fullform)"; if($mysqli->query($sql)){ printf("Procedure called successfully...!\n"); } //lets retirve the value variable using SELECT statement... $sql = "SELECT @fullform"; if($result = $mysqli->query($sql)){ printf("Variable value is: \n"); while($row = mysqli_fetch_array($result)){ print_r($row); } } if($mysqli->error){ printf("Error message: ", $mysqli->error); } $mysqli->close();

输出

获得的输出如下所示:

Resignal statement created successfully....!
Procedure called successfully...!
Variable value is: 
Array
(
   [0] => Bachelor of Science
   [@fullform] => Bachelor of Science
)   

var mysql = require('mysql2'); var con = mysql.createConnection({ host: "localhost", user: "root", password: "Nr5a0204@123" }); // Connecting to MySQL con.connect(function (err) { if (err) throw err; console.log("Connected!"); console.log("--------------------------"); // Create a new database sql = "Create Database TUTORIALS"; con.query(sql); sql = "USE TUTORIALS"; con.query(sql); // Create the example procedure var createProcedureSql = ` CREATE PROCEDURE example(IN degree VARCHAR(20), OUT full_form Varchar(50)) BEGIN IF degree='B-Tech' THEN SET full_form = 'Bachelor of Technology'; ELSEIF degree='M-Tech' THEN SET full_form = 'Master of Technology'; ELSEIF degree='BSC' THEN SET full_form = 'Bachelor of Science'; ELSEIF degree='MSC' THEN SET full_form = 'Master of Science'; ELSE RESIGNAL SQLSTATE '01000' -- Raise a warning SET MESSAGE_TEXT = 'Choose from the existing values', MYSQL_ERRNO = 12121; RESIGNAL SQLSTATE '45000' -- Raise an error SET MESSAGE_TEXT = 'Given degree is not valid', MYSQL_ERRNO = 1001; END IF; END; `; con.query(createProcedureSql, function (err) { if (err) throw err; console.log("Procedure example created!"); console.log("--------------------------"); }); //Passing BSC value to the procedure to get the fullform callExampleProcedureSql = "CALL example('BSC', @fullform);"; con.query(callExampleProcedureSql) selectFullFormSql = 'SELECT @fullform;'; con.query(selectFullFormSql, function (err, result) { if (err) throw err; console.log("Full form of degree:"); console.log(result); console.log("--------------------------"); }); //Passing an invalid value to the procedure callNonExistingProcedureSql = "CALL procedureEx ('BBC', @fullform);"; con.query(callNonExistingProcedureSql); con.query(selectFullFormSql, function (err, result) { if (err) throw err; console.log("Full form of BBC will leads to an error:"); console.log(result); con.end(); }); });

输出

获得的输出如下所示:

Connected!
--------------------------
Procedure example created!
--------------------------
Full form of degree:
[ { '@fullform': 'Bachelor of Science' } ]
--------------------------
C:\Users\Lenovo\desktop\JavaScript\connectDB.js:61
          if (err) throw err;
                             ^

Error: PROCEDURE tutorials.procedureEx does not exist
    at Packet.asError (C:\Users\Lenovo\desktop\JavaScript\node_modules\mysql2\lib\packets\packet.js:728:17)
    at Query.execute (C:\Users\Lenovo\desktop\JavaScript\node_modules\mysql2\lib\commands\command.js:29:26)
    at Connection.handlePacket (C:\Users\Lenovo\desktop\JavaScript\node_modules\mysql2\lib\connection.js:478:34)
    at PacketParser.onPacket (C:\Users\Lenovo\desktop\JavaScript\node_modules\mysql2\lib\connection.js:97:12)
    at PacketParser.executeStart (C:\Users\Lenovo\desktop\JavaScript\node_modules\mysql2\lib\packet_parser.js:75:16)
    at Socket. (C:\Users\Lenovo\desktop\JavaScript\node_modules\mysql2\lib\connection.js:104:25)
    at Socket.emit (node:events:513:28)
    at addChunk (node:internal/streams/readable:315:12)
    at readableAddChunk (node:internal/streams/readable:289:9)
    at Socket.Readable.push (node:internal/streams/readable:228:10)
Emitted 'error' event on Query instance at:
    at Query.execute (C:\Users\Lenovo\desktop\JavaScript\node_modules\mysql2\lib\commands\command.js:39:14)
    at Connection.handlePacket (C:\Users\Lenovo\desktop\JavaScript\node_modules\mysql2\lib\connection.js:478:34)
    [... lines matching original stack trace ...]
    at Socket.Readable.push (node:internal/streams/readable:228:10)
    at TCP.onStreamRead (node:internal/stream_base_commons:190:23) {
  code: 'ER_SP_DOES_NOT_EXIST',
  errno: 1305,
  sqlState: '42000',
  sqlMessage: 'PROCEDURE tutorials.procedureEx does not exist',
  sql: "CALL procedureEx ('BBC', @fullform);",
  fatal: true
}   
import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.Statement; public class Resignal { public static void main(String[] args) { String url = "jdbc:mysql://localhost:3306/TUTORIALS"; String user = "root"; String password = "password"; ResultSet rs; try { Class.forName("com.mysql.cj.jdbc.Driver"); Connection con = DriverManager.getConnection(url, user, password); Statement st = con.createStatement(); //System.out.println("Database connected successfully...!"); //lets generate error message using RESIGNAL statement String sql = "CREATE PROCEDURE example(IN degree VARCHAR(20), OUT full_form Varchar(50)) BEGIN IF degree='B-Tech' THEN SET full_form = 'Bachelor of Technology'; ELSEIF degree='M-Tech' THEN SET full_form = 'Master of Technology'; ELSEIF degree='BSC' THEN SET full_form = 'Bachelor of Science'; ELSEIF degree='MSC' THEN SET full_form = 'Master of Science'; ELSE RESIGNAL SQLSTATE '01000' SET MESSAGE_TEXT = 'Choose from the existing values', MYSQL_ERRNO = 12121; RESIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'Given degree is not valid', MYSQL_ERRNO = 1001; END IF; END"; st.execute(sql); System.out.println("Resignal statement created successfully....!"); //lets call the above procedure String sql1 = "CALL example('BSC', @fullform)"; st.execute(sql1); System.out.println("Procedure called successfully....!"); //lets retrieve the value variable using SELECT statement... String sql2 = "SELECT @fullform"; rs = st.executeQuery(sql2); System.out.println("variable value is: "); while(rs.next()) { String var = rs.getNString(1); System.out.println(var); } }catch(Exception e) { e.printStackTrace(); } } }

输出

获得的输出如下所示:

Resignal statement created successfully....!
Procedure called successfully....!
variable value is: 
Bachelor of Science
import mysql.connector # Establishing the connection connection = mysql.connector.connect( host='localhost', user='root', password='password', database='tut' ) # Creating a cursor object cursorObj = connection.cursor() # Using the RESIGNAL Statement to generate an error message resignal_statement = ''' CREATE PROCEDURE example(IN degree VARCHAR(20), OUT full_form VARCHAR(50)) BEGIN IF degree='B-Tech' THEN SET full_form = 'Bachelor of Technology'; ELSEIF degree='M-Tech' THEN SET full_form = 'Master of Technology'; ELSEIF degree='BSC' THEN SET full_form = 'Bachelor of Science'; ELSEIF degree='MSC' THEN SET full_form = 'Master of Science'; ELSE RESIGNAL SQLSTATE '01000' SET MESSAGE_TEXT = 'Choose from the existing values', MYSQL_ERRNO = 12121; RESIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'Given degree is not valid', MYSQL_ERRNO = 1001; END IF; END; ''' cursorObj.execute(resignal_statement) print("Stored procedure 'example' created successfully!") # Call the above procedure call = "CALL example('BSC', @fullform);" cursorObj.execute(call) print("Procedure 'example' called successfully!") # You can retrieve the value of the variable using SELECT statement retrieve = "SELECT @fullform;" cursorObj.execute(retrieve) result = cursorObj.fetchone() print("Retrieved full_form value:", result[0]) # If you pass an invalid value to the procedure, it will generate an error message pass_invalid = "CALL procedureEx ('BBC', @fullform);" try: cursorObj.execute(pass_invalid) except mysql.connector.Error as err: print("Error occurred:", err) # Closing the cursor and connection cursorObj.close() connection.close()

输出

获得的输出如下所示:

Stored procedure 'example' created successfully!
Procedure 'example' called successfully!
Retrieved full_form value: Bachelor of Science
Error occurred: 1305 (42000): PROCEDURE tut.procedureEx does not exist 
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