El-table sorting is useless

<el-table :data="bankLists" style="width: 100%" header-row-class-name="center" :default-sort="{prop: "createDate", order: "descending"}">
                <el-table-column prop="index" type="index" :index="indexMethod" width="50" label="" fixed>
                </el-table-column>
                <el-table-column prop="id" label="" width="50" fixed>
                </el-table-column>
                <el-table-column prop="interfaceNo" label="" width="100" fixed>
                </el-table-column>
                <el-table-column prop="remarks" label="" width="150" fixed>
                </el-table-column>
                <el-table-column prop="writer" label="" width="150" fixed>
                </el-table-column>
                <el-table-column prop="createDate" label="" width="100" >
                    <template slot-scope="scope">
                     {{scope.row.createDate|timeForm}}
                   </template>
                </el-table-column>

I want to descend by creation time, but table is still from index

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problem description

the environmental background of the problems and what methods you have tried

related codes

/ / Please paste the code text below (do not replace the code with pictures)

what result do you expect? What is the error message actually seen?

MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b3d580-2c392.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b3d580-2c392.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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