Microsoft SQL to MySQL trigger - mysql

Question

I need help with converting MS SQL command for trigger creation to similar command in MySQL. It works fine in MS SQL but I know nothing of MySQL.
The command is as it follows:
USE [Project]
GO
/****** Object: Trigger [General].[TR_tblFirmaZaposleni_U] Script Date: 7.1.2014 17:47:35 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TRIGGER [General].[TR_tblFirmaZaposleni_U]
ON [General].[tblFirmaZaposleni]
FOR UPDATE
AS UPDATE [General].[tblFirmaZaposleni]
SET [A_tblFirmaZaposleniUpdatedBy] = SUBSTRING(SUSER_SNAME(),(CHARINDEX('\',SUSER_SNAME()) + 1),LEN(SUSER_SNAME())), [A_tblFirmaZaposleniUpdatedOn] = GetDate()
FROM [General].[tblFirmaZaposleni] s
INNER JOIN [INSERTED] i ON s.[ZaposleniID] = i.[ZaposleniID]
INSERT INTO ProjectAudit.[General].[tblFirmaZaposleni] SELECT 'B','U',* FROM DELETED
INSERT INTO ProjectAudit.[General].[tblFirmaZaposleni] SELECT 'A','U',* FROM INSERTED
GO

Answer 1

Despite their apparent similarities, SQL Server and MySQL are actually very different products: each of which deviate from the SQL standards in different ways. Indeed, the divergence significantly widens as one delves deeper into their features and functionality.
Thus there is not a 1:1 mapping between what you have in SQL Server and what can be done in MySQL. You would do well to read around on the differences between the systems and how migrations can best be managed. It may well be that significant elements of application design should be engineered specifically to take advantage (or overcome lacks) of features or functionality that exist in one system or the other.
To the extent that you do keep the databases similar, an equivalent set of commands in MySQL would look something like this:
USE Project
DELIMITER ;;
CREATE TRIGGER TR_tblFirmaZaposleni_U
BEFORE UPDATE ON tblFirmaZaposleni
FOR EACH ROW BEGIN
SET NEW.A_tblFirmaZaposleniUpdatedBy = SUBSTRING_INDEX(CURRENT_USER, '#', 1),
NEW.A_tblFirmaZaposleniUpdatedOn = CURRENT_DATE;
INSERT INTO ProjectAudit.tblFirmaZaposleni VALUES
('B','U', OLD.colA, OLD.colB, OLD.colC, ....),
('A','U', NEW.colA, NEW.colB, NEW.colC, ....);
END;;
It may be worth noting that, like SUSER_SNAME() in SQL Server, CURRENT_USER in MySQL returns the user as which the trigger is running, rather than the user as which the client was authenticated. You may wish to use MySQL's USER() function instead.
It may also be worth noting that MySQL offers Automatic Initialization and Updating for TIMESTAMP and DATETIME, which saves you having to set such values within a trigger.
As for the initial SET statements (which have no effect on the trigger), MySQL has no equivalent to SQL Server's ANSI_NULLS setting but you can set its ANSI_QUOTES SQL mode if you wish to achieve the same effect as setting SQL Server's QUOTED_IDENTIFIER.