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How is it possible for a MySQL trigger to execute multiple statements?

I want to create MySQL trigger but I want that it should execute more than one statement. Is it possible to execute multiple statements by the MySQL trigger?
George John
Answered on 22nd Feb, 2018

The MySQL trigger can execute multiple statements with the help of BEGIN…END construct. Within the BEGIN block, we can also use another syntax that is permitted within stored routines such as conditionals and loops. For illustrating the concept, we are using the following example of BEFORE INSERT TRIGGER is having ... Read More

How can we escape special characters in MySQL statement?

I am having a character string with special character. I want to know about the way to protect these special characters.
Nishtha Thakur
Answered on 22nd Feb, 2018

Sometimes we need to include special characters in a character string and at that time they must be escaped or protected. We need to pursue some basic rules for escaping special characters which are given below:The escape character (\) can be escaped as (\\).Examplemysql> Select 'A\\B'; +-----+ | A\B | ... Read More

How can we see the information on triggers order in case of multiple triggers for same event and action time?

I have created multiple triggers for the same event and action time. Is it possible to check the details on trigger order i.e. which trigger would be executed first and which would be executed .....
karthikeya Boyini
Answered on 22nd Feb, 2018

It can be done with the help of the following query:mysql> SELECT trigger_name, action_order FROM INFORMATION_SCHEMA.triggers WHERE TRIGGER_SCHEMA = 'query' ORDER BY event_object_table, action_timing, event_manipulation; +------------------------------+--------------+ | trigger_name                 | action_order | +------------------------------+--------------+ | studentdetail_before_update  |            1 | ... Read More

How can we create multiple MySQL triggers for the same trigger event and action time?

In MySQL, is it possible to create multiple MySQL triggers for the same trigger event and action time?
Ayyan
Answered on 22nd Feb, 2018

MySQL 5.7.2+ allows us to create multiple triggers for the same event and action time in a table. Both the triggers will activate sequentially when the event occurs. It can be understood with the help of an example:ExampleIn this example,  we are creating multiple triggers for the same event say ... Read More

In which order MySQL will invoke the triggers if we created multiple triggers of same event and action time?

I have created multiple triggers for the same event and action time then which trigger would be executed first and which would be executed next?
Chandu yadav
Answered on 22nd Feb, 2018

In this case, MySQL will invoke the triggers in the order in which they are created. But with the help of following options we can change the order:FOLLOWS optionThis option allows the new trigger to activate after the existing trigger.SyntaxFOR EACH ROW FOLLOWS trigger_namePRECEDES optionThis option allows the new trigger ... Read More

How can I check the tables of databases other than current database?

I want to check the list of tables stored in MySQL database other than the current database i.e. the default database I am using.
Giri Raju
Answered on 22nd Feb, 2018

With the help of following MySQL command we can check the tables of a database other than the database we are currently using:Show Tables from Database_name;For example, the following query would display the list of tables from a database named ‘gaurav’ when currently we are using a database named ‘new’:mysql> ... Read More

What are the several ways to add comments in MySQL query?

I want to add some comments while creating a MySQL table. How can I do this?
Priya Pallavi
Answered on 22nd Feb, 2018

We can add comments in the several ways which are supported by MySQL server:# CommentThis is a single line comment. This kind of comment starts with a # character and until the end of the line.-– Comment This is also a single line comment. It must be followed by space or ... Read More

Why do we need to change the delimiter for creating a trigger?

I have seen that before creating the trigger we used to change the delimiter from semicolon (;) to some other special character like $$ or // etc. Why is it so?
Swarali Sree
Answered on 22nd Feb, 2018

As we know that in MySQL we use the delimiter semicolon (;) to end each statement. The semicolon is the by default delimiter in MySQL. We need to change the delimiter, while creating a trigger, to tell MySQL that this is not the end of our trigger statement because we ... Read More

How can I get the records from MySQL table in result set in a particular way?

I have a MySQL table with many values but those values are not in any sorted manner. Which MySQL statement I can use to sort the data of the result set from that MySQL table in a particular man.....
Sreemaha
Answered on 22nd Feb, 2018

For getting the records from MySQL table in the result set in a particular way either ascending or descending, we need to use ORDER BY clause along with ASC or DESC keywords. If we will not use any of the above-mentioned keywords then MySQL by default return the records in ... Read More

How OLD and NEW keywords enable us to access columns in row affected by a trigger?

While creating a MySQL trigger what is the use of OLD and NEW keywords?
Sai Subramanyam
Answered on 22nd Feb, 2018

As we know that in trigger definition, we can refer to columns of the row being inserted, updated or deleted. Following are the ways OLD and NEW keywords enable us to access columns − We must have to prefix the column name with a qualifier of OLD to refer ... Read More

How Can we use MySQL DISTINCT clause with WHERE and LIMIT clause?

While getting the list of unique values from MySQL table, I want to put some sort of conditions on the result set so is it possible to use WHERE clause with MySQL DISTINCT clause?
Nikitha N
Answered on 22nd Feb, 2018

By using WHERE clause with a DISTINCT clause in MySQL queries, we are putting a condition on the basis of which MySQL returns the unique rows of the result set. By using the LIMIT clause with a DISTINCT clause in MySQL queries, we are actually providing a perimeter to the ... Read More

Can we use MySQL GROUP BY clause with multiple columns like MySQL DISTINCT clause is used?

I want to use the combination of more than one column while using the MySQL GROUP BY clause.
varma
Answered on 22nd Feb, 2018

Yes, it is possible to use MySQL GROUP BY clause with multiple columns just as we can use MySQL DISTINCT clause. Consider the following example in which we have used DISTINCT clause in first query and GROUP BY clause in the second query, on ‘fname’ and ‘Lname’ columns of the ... Read More

What happens with the trigger when we will drop the table having that trigger?

Suppose if we have a MySQL table and there is a MySQL trigger which is related to this particular table. I want to drop this table but before this want to know that what would happen to the ass.....
Rama Giri
Answered on 22nd Feb, 2018

The trigger would also be destroyed if we will destroy the table with which it is associated. It is called the explicit destroy of a trigger. It can be understood with the help of an example:ExampleSuppose we have a trigger named ‘trigger_before_delete_sample’ on the table named ‘Sample’. Now if we will delete ... Read More

How we can find all the triggers associated with a particular MySQL table?

I want to get the list of all triggers that are created on a particular MySQL table say ‘ABC’.
Maheshwari Thakur
Answered on 22nd Feb, 2018

We can find all the triggers associated with a particular table with the help of the following query:mysql> Select * from INFORMATION_SCHEMA.TRIGGERS WHERE TRIGGER_SCHEMA = 'query'AND EVENT_OBJECT_TABLE = 'Student_info'\G *************************** 1. row ***************************            TRIGGER_CATALOG: def             TRIGGER_SCHEMA: query       ... Read More

How Can MySQL GROUP BY clause behave like DISTINCT clause?

I want to get the unique values from MySQL table but do not want to use DISTINCT clause. Is it possible to do?
Srinivas Gorla
Answered on 22nd Feb, 2018

When we use GROUP BY clause in the SELECT statement without using aggregate functions then it would behave like DISTINCT clause. For example, we have the following table:mysql> Select * from testing; +------+---------+---------+ | id   | fname   | Lname   | +------+---------+---------+ |  200 | Raman   | ... Read More

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