What can not have a trigger in MySQL?

What Cannot have a trigger?

Since triggers execute as part of a transaction, the following statements are not allowed in a trigger: All create commands, including create database, create table, create index, create procedure, create default, create rule, create trigger, and create view. All drop commands. alter table and alter database.

Can we use triggers in MySQL?

MySQL supports triggers that are invoked in response to the INSERT , UPDATE or DELETE event. The SQL standard defines two types of triggers: row-level triggers and statement-level triggers.

What are triggers used for MySQL?

A trigger is a named database object that is associated with a table, and that activates when a particular event occurs for the table. Some uses for triggers are to perform checks of values to be inserted into a table or to perform calculations on values involved in an update.

Which of the following MySQL routine will not execute statements?

Stored routines cannot contain arbitrary SQL statements. The following statements are not permitted: The locking statements LOCK TABLES and UNLOCK TABLES . ALTER VIEW .

What are the types of triggers?

Types of Triggers

  • Data Manipulation Language (DML) Triggers. DML triggers are executed when a DML operation like INSERT, UPDATE OR DELETE is fired on a Table or View. …
  • Data Definition Language (DDL) Triggers. …
  • LOGON Triggers. …
  • CLR Triggers.
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How do I run a trigger in PL SQL?

Syntax for creating trigger:

  1. CREATE [OR REPLACE ] TRIGGER trigger_name.
  2. {BEFORE | AFTER | INSTEAD OF }
  3. {INSERT [OR] | UPDATE [OR] | DELETE}
  4. [OF col_name]
  5. ON table_name.
  6. [REFERENCING OLD AS o NEW AS n]
  7. [FOR EACH ROW]
  8. WHEN (condition)

What triggers SQL?

A trigger is a special type of stored procedure that automatically runs when an event occurs in the database server. DML triggers run when a user tries to modify data through a data manipulation language (DML) event. DML events are INSERT, UPDATE, or DELETE statements on a table or view.

Why MyISAM gives the best performance?

MyISAM is designed with the idea that your database is queried far more than its updated and as a result it performs very fast read operations. If your read to write(insert|update) ratio is less than 15% its better to use MyISAM.

What is MySQL interview questions?

Basic MySQL Interview Questions

  • What is MySQL? MySQL is a database management system for web servers. …
  • What are some of the advantages of using MySQL? …
  • What do you mean by ‘databases’? …
  • What does SQL in MySQL stand for? …
  • What does a MySQL database contain? …
  • How can you interact with MySQL? …
  • What are MySQL Database Queries?

How do I trigger a MySQL database?

How to create triggers in MySQL?

  1. CREATE TRIGGER trigger_name.
  2. (AFTER | BEFORE) (INSERT | UPDATE | DELETE)
  3. ON table_name FOR EACH ROW.
  4. BEGIN.
  5. –variable declarations.
  6. –trigger code.
  7. END;

Are MySQL triggers fast?

It looks like TRIGGER s are more efficient for logging than doing it manually in the application. If MySQL Stored Language is NOT used for computational tasks but for SQL tasks the performance might be OK.

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How do I run a trigger in MySQL?

How can we create and use a MySQL trigger?

  1. Trigger_name is the name of the trigger which must be put after the CREATE TRIGGER statement. …
  2. Trigger_time is the time of trigger activation and it can be BEFORE or AFTER. …
  3. Trigger_event can be INSERT, UPDATE, or DELETE. …
  4. Table_name is the name of the table. …
  5. BEGIN…

What is prepare statement in MySQL?

The MySQL database supports prepared statements. A prepared statement or a parameterized statement is used to execute the same statement repeatedly with high efficiency and protect against SQL injections. … The server executes the statement with the bound values using the previously created internal resources.

What is difference between stored procedure and function?

The function must return a value but in Stored Procedure it is optional. Even a procedure can return zero or n values. Functions can have only input parameters for it whereas Procedures can have input or output parameters. Functions can be called from Procedure whereas Procedures cannot be called from a Function.

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