What is Apex Triggers.? Why we Use? What is Syntex? What is Events? What is Context Variable? What is bulkify triggers?

➡️ Apex Triggers:-

-> This is automation tool. Apex triggers enable you to perform custom actions before or after changes to Salesforce records, such as insertions, updates, or deletions.

-> It executes before or after the following types of operations:

• Insert
• Update
• Delete
• Upsert
• Undelete
• Merge

📌Important:-

-> Don't Query and DML Operation in the Loop.

-> Apex trigger can be created for both standard & custome objects.

-> By default trigger are active as you create them.

-> We can make sure our trigger is always bulkify.

➡️ Why we use Apex Triggers?

-> When we are not abel to solve some complex requirements throuth Salesforce Point and Click tools (Flows, PB, WF) then we can use apex triggers.

➡️ Types of Apex Triggers:-

=> There are two types of triggers.

-> Before triggers are used to update or validate record values before they’re saved to the database.

-> After triggers are used to access field values that are set by the system (such as a record's Id or LastModifiedDate field), and to affect changes in other records. The records that fire the after trigger are read-only.

➡️ Apex Triggers Events:-

=> There are 7 types of events.

• Before Insert
• Before Update
• Before Delete
• ------------------
• After Insert 
• After Update
• After Delete
• After Undelete

➡️ Apex Triggers Context Variables:-

=> There are following type of context variables in trigger

• Trigger.new Returns a list of the new versions of the sObject records. This sObject list is only available in Insert , update, and undelete triggers, and the records can only be modified in Before triggers.
• Trigger.old Returns a list of the old versions of the sObject records. This sObject list is only available in update and delete triggers.
• Trigger.isInsert Returns true if this trigger was fired due to an insert operation, from the Salesforce user interface, Apex, or the API. 
• Trigger.isUpdate Returns true if this trigger was fired due to an update operation, from the Salesforce user interface, Apex, or the API.
• Trigger.isDelete Returns true if this trigger was fired due to a delete operation, from the Salesforce user interface, Apex, or the API.
• Trigger.isBefore Returns true if this trigger was fired before any record was saved.
• Trigger.isAfter Returns true if this trigger was fired after all records were saved.
• Trigger.isUndelete Returns true if this trigger was fired after a record is recovered from the Recycle Bin. This recovery can occur after an undelete operation from the Salesforce user interface, Apex, or the API.
• Trigger.newMap A map of IDs to the new versions of the sObject records This map is only available in before update, after insert, after update, and after undelete triggers.
• Trigger.oldMap A map of IDs to the old versions of the sObject records. This map is only available in 
• Trigger.size The total number of records in a trigger invocation, both old and new.
• Trigger.isExecuting Returns true if the current context for the Apex code is a trigger, not a Visualforce page, a Web service, or an executeanonymous() API call.

➡️ What is Bulkify Apex Triggers?

-> Bulk triggers can handle both single record updates and bulk operations like: Data import. Lightning Platform Bulk API calls. Mass actions, such as record owner changes and deletes.

➡️ Apex Triggers Syntex:-

    trigger TriggerName on ObjectName (trigger_events1,trigger_events2) {
                     //your code blocks..
     }