How to implement Roll Back Transaction and Error Message in MYSQL

问题

I Have sample procedure .

CREATE PROCEDURE `sample_procedure ` 
(
IN IDIn bigint(20),
IN MainIDIn bigint(20),
IN NameIn  varchar(20)
)
 READS SQL DATA
    DETERMINISTIC
BEGIN
INSERT INTO tbl_DEPT
(
ID,
Name)
Select 1,'Mohan';

IF NOT EXISTS (SELECT ID FROM tbl_emp  te  WHERE te.ID = IDIn) THEN 
INSERT INTO tbl_emp
(
MainID,
Name) 
VALUES (MainIDIn,
        NameIn);
ELSE 
IF  EXISTS (SELECT ID FROM tbl_emp  te  WHERE te.ID = IDIn) THEN 
  UPDATE tbl_emp  
  set
    MainID =MainIDIn,
    name = NameIn
  WHERE te.ID= IDIn;
  END IF;
  END IF;
END

Call sample_procedure(1,2,Sampl123)

I'm just sending some irrelevant Data into the Procedure so that procedure gets failed . But how we need to implement roll back means it should come to the starting state with out Inserting Records into the tbl_DEPT also.

IN T-SQL we will have

BEGIN
    SET NOCOUNT ON
    BEGIN TRANSACTION
    BEGIN TRY
        SET @OUT = "success";
        COMMIT TRANSACTION
    END TRY

    BEGIN CATCH
        set @out = 'not success';
        ROLLBACK TRANSACTION
    END CATCH
END

this kind of TRY CATCH blocks and to capture Error

 "ERROR_NUMBER() AS ErrorNumber,
    ERROR_SEVERITY() AS ErrorSeverity"

In the same way in MYSQL I'm looking for TRY CATCH and ROLL BACK Mechanism .

IF Procedure fails it should ROLL BACK and Not to load in any of the table .

Can any one Suggest me in MYSQL.

回答1:

Mysql does not use try/catch. If uses handlers, e.g. the EXIT handler that will terminate the execution of the SP:

DECLARE EXIT HANDLER FOR SQLEXCEPTION 
BEGIN 
    ROLLBACK;
    -- other logic
END;

There are other type of handlers as well.

来源：https://stackoverflow.com/questions/61481328/how-to-implement-roll-back-transaction-and-error-message-in-mysql

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mysql

sql