[Solidity] How to delete an element of a mapping?

This section explains how to delete mapping element in Solidity.

Syntax

To delete a mapping element in Solidity, use the delete operator.

delete Mapping Variable[key];

Sample Code

// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.7.0 <0.9.0;

contract Test {
    
    mapping (address => uint) public balances;
    
    function store(uint256 num) public {
        balances[msg.sender] = num;
    }

    function deleteElement(address _address) public {
        // Delete mapping element
        delete balances[_address];
    }

    function retrieve() public view returns (uint256){
        return balances[msg.sender];
    }

}

Deleting an element with the delete operator will only result in 0 being stored. Note that the element itself is not deleted, and the number of elements itself remains unchanged.