How to fetch data from Controller and display it in Visualforce page without using button?

To fetch data from Controller and display it in Visualforce page without using button, retrieve the record in the constructor.

Sample code:

Visualforce page:

<apex:page controller="Sample" >
    <apex:form >
       <apex:pageblock id="account" title="Account Details(Standard Object)" >
            <apex:pageblockTable value="{!acc}" var="a">
                <apex:column value="{!a.Name}"/>
                <apex:column value="{!a.AccountNumber}"/>
            </apex:pageblockTable>
        </apex:pageblock>
       <apex:pageblock id="member" title="Member Details(Custom Object)">
            <apex:pageblockTable value="{!mem}" var="m">
                <apex:column value="{!m.Name}"/>
            </apex:pageblockTable>         
        </apex:pageblock>          
    </apex:form>
</apex:page>

Controller:

public with Sharing class Sample
{   
    public List<Account> acc {get;set;}
    public List<Member__c> mem {get;set;}   
      
    public sample()
    {
        acc = [SELECT Name, AccountNumber FROM Account];
        mem = [SELECT Name FROM Member__c];
    }
}

Output: