as the title

!important

but if I write this, I can overwrite the following, which can take effect. Is there a big god to explain?
ask for a big god answer

I posted the whole code

< html lang= "en" >

< head >

<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<script src="https://unpkg.com/vue"></script>
<link rel="stylesheet" href="./test.less">
<!--  -->
<link rel="stylesheet" href="https://unpkg.com/element-ui/lib/theme-chalk/index.css">
<!--  -->
<script src="https://unpkg.com/element-ui/lib/index.js"></script>
<script src="https://unpkg.com/vue/dist/vue.js"></script>
<script src="https://unpkg.com/element-ui@2.0.8/lib/index.js"></script>

< / head >

< body >

<div id="app">
    <template>
        <el-table :data="tableData2" style="width: 100%" :row-class-name="tableRowClassName" :header-row-class-name="demo" border :header-row-class-name="demo">
            <el-table-column prop="date" label="" width="180">
            </el-table-column>
            <el-table-column prop="name" label="" width="180">
            </el-table-column>
            <el-table-column prop="address" label="">
            </el-table-column>
        </el-table>
    </template>
</div>

<style>
    .el-table .warning-row {
        background: oldlace;
    }

    .el-table .success-row {
        background: -sharpf0f9eb;
    }

    .el-table th, .el-table tr.demo {
        background-color: -sharp0f0!important;
    }
    /* .el-table th, .el-table tr.demo{
        background: red;
    } */

</style>

<script>
    var Main = {
        methods: {
            tableRowClassName({
                row,
                rowIndex
            }) {
                if (rowIndex === 1) {
                    return "warning-row";
                } else if (rowIndex === 3) {
                    return "success-row";
                }
                return "";
            },
            demo({row, rowIndex}){
                return "demo";
            }
        },
        data() {
            return {
                tableData2: [{
                    date: "2016-05-02",
                    name: "",
                    address: " 1518 ",
                }, {
                    date: "2016-05-04",
                    name: "",
                    address: " 1518 "
                }, {
                    date: "2016-05-01",
                    name: "",
                    address: " 1518 ",
                }, {
                    date: "2016-05-03",
                    name: "",
                    address: " 1518 "
                }]
            }
        }
    }
    var Ctor = Vue.extend(Main)
    new Ctor().$mount("-sharpapp")
</script>

< / body >

< / html >