Trigger updating column

If you specify the DEFINER clause, these rules determine the valid DEFINER user values: trigger_name: All triggers must have unique names within a schema.

trigger updating column-89trigger updating column-71

It can be BEFORE or AFTER to indicate that the trigger activates before or after each row to be modified.

(Such a SET statement has no effect in an AFTER trigger because the row change will have already occurred.) Sample database, table, table structure, table records for various examples Database Name: hr Host Name : localhost Database user : root Password : ' ' Structure of the table : emp_details Records of the table (on some fields): emp_details SELECT EMPLOYEE_ID, FIRST_NAME, LAST_NAME, JOB_ID, SALARY, COMMISSION_PCT FROM emp_details; ------------- ------------ ----------- --------- ---------- ---------------- | EMPLOYEE_ID | FIRST_NAME | LAST_NAME | JOB_ID | SALARY | COMMISSION_PCT | ------------- ------------ ----------- --------- ---------- ---------------- | 100 | Steven | King | AD_PRES | 24000.00 | 0.10 | | 101 | Neena | Kochhar | AD_VP | 17000.00 | 0.50 | | 102 | Lex | De Haan | AD_VP | 17000.00 | 0.50 | | 103 | Alexander | Hunold | IT_PROG | 9000.00 | 0.25 | | 104 | Bruce | Ernst | IT_PROG | 6000.00 | 0.25 | | 105 | David | Austin | IT_PROG | 4800.00 | 0.25 | ------------- ------------ ----------- --------- ---------- ---------------- 6 rows in set (0.00 sec) Tool to create My SQL Triggers You can write a procedure in My SQL command line tool or you can use My SQL workbench which is an excellent front-end tool (here we have used version 5.3 CE). PER_MARKS SELECT * FROM STUDENT_MARKS; ------------ ------------------ ------ ------ ------ ------ ------ ------- ----------- ------- | STUDENT_ID | NAME | SUB1 | SUB2 | SUB3 | SUB4 | SUB5 | TOTAL | PER_MARKS | GRADE | ------------ ------------------ ------ ------ ------ ------ ------ ------- ----------- ------- | 1 | Steven King | 54 | 69 | 89 | 87 | 59 | 358 | 71.60 | GOOD | | 2 | Neena Kochhar | 0 | 0 | 0 | 0 | 0 | 0 | 0.00 | | | 3 | Lex De Haan | 0 | 0 | 0 | 0 | 0 | 0 | 0.00 | | | 4 | Alexander Hunold | 0 | 0 | 0 | 0 | 0 | 0 | 0.00 | | ------------ ------------------ ------ ------ ------ ------ ------ ------- ----------- ------- 4 rows in set (0.00 sec) My SQL Trigger : Example AFTER DELETE In our 'AFTER UPDATE' example, we had two tables student_mast and stu_log.

My SQL command line tool: - Select My SQL command Client from Start menu: Selecting My SQL command prompt following screen will come: After a successful login, you can access the My SQL command prompt: Now you can write your own trigger on a specific table, see the following example : My SQL workbench (5.3 CE): - Select My SQL workbench from Start menu : After selecting My SQL workbench following login screen will come: Now input the login details : After successful login, a new screen will come and from the tab in the previous section, then select the Timing/Event it may be AFTER DELETE, AFTER INSERT, AFTER UPDATE or BEFORE DELETE, BEFORE INSERT OR BEFORE UPDATE. student_mast have three columns STUDENT_ID, NAME, ST_CLASS and stu_log table has two columns user_id and description.

For this sample calculation, the following conditions are assumed : Total Marks (will be stored in TOTAL column) : TOTAL = SUB1 SUB2 SUB3 SUB4 SUB5 Percentage of Marks (will be stored in PER_MARKS column) : PER_MARKS = (TOTAL)/5 Grade (will be stored GRADE column) : - If PER_MARKSUSE `test`; DELIMITER $$ CREATE TRIGGER `student_marks_BUPD` BEFORE UPDATE ON student_marks FOR EACH ROW -- Edit trigger body code below this line.

The CREATE TRIGGER statement has a lot of permutations, but the vast majority of the questions I'm asked relate to basic DML triggers.

5 comments

  1. Triggers are database operations that are automatically performed when a specified database event occurs. A trigger may be specified to fire whenever a DELETE, INSERT, or UPDATE of a particular database table occurs, or whenever an UPDATE occurs on on one or more specified columns of a table. At this time SQLite.

Leave a Reply

Your email address will not be published. Required fields are marked *

*