在开始之前先要明确几个概念：
保持不变：{ rowspan: 1, colspan: 1 }
删除一个单元格：{ rowspan: 0, colspan: 0 }
合并一个单元格：{ rowspan: 2, colspan: 1 }

<template><div><el-table:data="tableData":span-method="mergeSpanMethod"border:header-cell-style="{ textAlign: 'center', backgroundColor: '#F5F7FA' }"><el-table-column prop="School" label="学校" align="center" /><el-table-column prop="Chinese" label="语文" align="center" /><el-table-column prop="Math" label="数学" align="center" /><el-table-column prop="English" label="英语" align="center" /></el-table></div>
</template>
<script>
export default {name: 'HelloWorld',data() {return {tableData: [{School: "第1小学",Chinese: "180",Math: 0,English: "180"},{School: "第1小学",Chinese: 0,Math: 0,English: "180"},{School: "第2小学",Chinese: "290",Math: "200",English: "180"},{School: "第2小学",Chinese: "295",Math: "200",English: "280"},{School: "第3小学",Chinese: "398",Math: "385",English: "380"},{School: "第3小学",Grade: "2年级",Chinese: "398",Math: "100",English: "80"},{School: "第4小学",Grade: "3年级",Chinese: "91",Math: 0,English: "80"},{School: "第4小学",Grade: "3年级",Chinese: "91",Math: 0,English: "87"},{School: "第5小学",Grade: "3年级",Chinese: "79",Math: 0,English: "80"}],};},props: {msg: String},mounted() {},methods: {mergeSpanMethod({ row, column, rowIndex, columnIndex }) {// 如果某些列不需要合并， 在此排除if (columnIndex === 1) return {rowspan: 1, colspan: 1};// 两两对比 相同的列合并const num = 2;const times = Math.ceil(this.tableData.length / num);for (let k = 0 ; k < times; k++) {const one = k * num;const two = k * num + 1;if (rowIndex === one || rowIndex === two) {const currentValue = row[column.property];const arr = [this.tableData[one], this.tableData[two]];// 获取上一行相同列的值const preRow = arr[rowIndex - 1 - (k * num)];const preValue = preRow ? preRow[column.property] : null;// 如果当前值和上一行的值相同，则将当前单元格隐藏if (currentValue === preValue) {return { rowspan: 0, colspan: 0 };} else {let rowspan = 1;for (let i = (rowIndex - (k * num)) + 1; i < arr.length; i++) {const nextRow = arr[i];const nextValue = nextRow ? nextRow[column.property] : null;if (nextValue === currentValue) {rowspan++;} else {break;}}return { rowspan, colspan: 1 };}}}return {rowspan: 1, colspan: 1};// 这下面是在解题时的思路，也是一步步的慢慢推导出来的// 先写死数据一组组的对比，再从中找共性，如果上面看不懂，可以把上面注释，解开下面 就明白了// if (rowIndex === 0 || rowIndex === 1) {//   const currentValue = row[column.property];//   const arr = [this.tableData[0], this.tableData[1]];//   // 获取上一行相同列的值//   const preRow = arr[rowIndex - 1];//   const preValue = preRow ? preRow[column.property] : null;////   // 如果当前值和上一行的值相同，则将当前单元格隐藏//   if (currentValue === preValue) {//     return { rowspan: 0, colspan: 0 };//   } else {//     let rowspan = 1;//     for (let i = rowIndex + 1; i < arr.length; i++) {//       const nextRow = arr[i];//       const nextValue = nextRow[column.property];//       if (nextValue === currentValue) {//         rowspan++;//       } else {//         break;//       }//     }//     return { rowspan, colspan: 1 };//   }// }// if (rowIndex === 2 || rowIndex === 3) {//   const currentValue = row[column.property];//   const arr = [this.tableData[2], this.tableData[3]];////   const preRow = arr[rowIndex - 1 - 2];//   const preValue = preRow ? preRow[column.property] : null;////   // 如果当前值和上一行的值相同，则将当前单元格隐藏//   if (currentValue === preValue) {//     return { rowspan: 0, colspan: 0 };//   } else {//     let rowspan = 1;//     for (let i = (rowIndex - 2) + 1; i < arr.length; i++) {//       const nextRow = arr[i];//       const nextValue = nextRow[column.property];//       if (nextValue === currentValue) {//         rowspan++;//       }//     }//     return { rowspan, colspan: 1 };//   }// }// if (rowIndex === 4 || rowIndex === 5) {//   const currentValue = row[column.property];//   const arr = [this.tableData[4], this.tableData[5]];////   const preRow = arr[rowIndex - 1 - 4];//   const preValue = preRow ? preRow[column.property] : null;////   // 如果当前值和上一行的值相同，则将当前单元格隐藏//   if (currentValue === preValue) {//     return { rowspan: 0, colspan: 0 };//   } else {//     let rowspan = 1;//     for (let i = (rowIndex - 4) + 1; i < arr.length; i++) {//       const nextRow = arr[i];//       const nextValue = nextRow[column.property];//       if (nextValue === currentValue) {//         rowspan++;//       }//     }//     return { rowspan, colspan: 1 };//   }// }// console.log('rowIndex', rowIndex);// return {rowspan: 1, colspan: 1}}}
}
</script>

如果需要所有的列都对比合并单元格可以看下面的文章
element + table 行列合并