public class DatatableCheckboxC {
    
    @AuraEnabled
    public static List<Account> fetch(){
        List<Account> acc = [SELECT Name, Phone, Rating FROM Account LIMIT 20];
        return acc;
    }
    
    @AuraEnabled
    public static void deleteForm(List<Account> lstId) {
        List<Account> rf = [SELECT Id FROM Account WHERE Id IN :lstId];
        delete rf;
    }
}

<aura:component controller="DatatableCheckboxC"
                implements="force:appHostable,flexipage:availableForAllPageTypes,flexipage:availableForRecordHome,force:hasRecordId,forceCommunity:availableForAllPageTypes,force:lightningQuickAction" 
                access="global" >
    
    <aura:attribute name="PageHeading" type="String" default="Delete Records"/>
    <aura:attribute name="mydata" type="Object"/>
    <aura:attribute name="mycolumns" type="List"/>
    <aura:attribute name="delIds" type="List"/>
    
    <aura:handler name="init" value="{!this}" action="{!c.init}" />
    <aura:handler event="force:refreshView" action="{!c.init}" />
    
    <div class="slds-m-top--xx-large">
        <div class="slds-page-header">
            <div class="slds-align--absolute-center">
                <div class="slds-text-heading--large">       
                    {!v.PageHeading}
                </div>
            </div>
        </div>
    </div>
    <br/> <br/>
    
    <div class="slds-grid slds-grid--align-end"> 
        <lightning:button variant="brand" label="Delete" onclick="{!c.doDelete}"/>
    </div>
    <lightning:datatable data="{! v.mydata }" 
                         columns="{! v.mycolumns }" 
                         keyField="Id" 
                         onrowselection="{! c.handleRowAction }"/>
</aura:component>

({
    init : function(component, event, helper) {
        component.set('v.mycolumns', [
            {label: 'Account Name', fieldName: 'Name', type: 'text'},
            {label: 'Phone', fieldName: 'Phone', type: 'phone'},
            {label: 'Rating', fieldName: 'Rating', type: 'text'}
        ]);
        
        var action = component.get("c.fetch");
        action.setCallback(this, function(response) {
            var state = response.getState();
            if (state === "SUCCESS") {
                console.log(response.getReturnValue());
                component.set("v.mydata", response.getReturnValue());
            }
            else if (state === "ERROR") {
                var errors = response.getError();
                if (errors) {
                    if (errors[0] && errors[0].message) {
                        console.log("Error message: " + 
                                    errors[0].message);
                    }
                } 
                else {
                    console.log("Unknown Error");
                }
            }
        });
        $A.enqueueAction(action);
    },
    
    handleRowAction : function(component, event, helper){
        var selRows = event.getParam('selectedRows');
        component.set("v.delIds",selRows);
    },
    
    doDelete : function(component, event, helper){
        var delIdList = component.get("v.delIds");
        var action = component.get('c.deleteForm');
        action.setParams({lstId : delIdList});
        action.setCallback(this, function(response) {
            var state = response.getState();
            if (state === "SUCCESS") {
                $A.get('e.force:refreshView').fire();
                alert('Successfully Deleted');   
            }
            else if (state === "ERROR") {
                var errors = response.getError();
                if (errors) {
                    if (errors[0] && errors[0].message) {
                        console.log("Error message: " + 
                                    errors[0].message);
                    }
                } 
                else {
                    console.log("Unknown Error");
                }
            }
        });
        $A.enqueueAction(action);
    },
})