sequelize外键关联报错SequelizeDatabaseError: Cant write; duplicate key in table #sql-454_d

ALTER TABLE `assistance` ADD CONSTRAINT `assistance_user_id_foreign_idx` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE NO ACTION ON UPDATE CASCADE;

Unhandled rejection SequelizeDatabaseError: Can't write; duplicate key in table '#sql-454_d'
    at Query.formatError (/home/hale/workspace/issue-tracking-system/node_modules/sequelize/lib/dialects/mysql/query.js:223:16)
    at Query.connection.query [as onResult] (/home/hale/workspace/issue-tracking-system/node_modules/sequelize/lib/dialects/mysql/query.js:55:23)
    at Query.Command.execute (/home/hale/workspace/issue-tracking-system/node_modules/mysql2/lib/commands/command.js:30:12)
    at Connection.handlePacket (/home/hale/workspace/issue-tracking-system/node_modules/mysql2/lib/connection.js:515:28)
    at PacketParser.onPacket (/home/hale/workspace/issue-tracking-system/node_modules/mysql2/lib/connection.js:94:16)
    at PacketParser.executeStart (/home/hale/workspace/issue-tracking-system/node_modules/mysql2/lib/packet_parser.js:77:14)
    at Socket.<anonymous> (/home/hale/workspace/issue-tracking-system/node_modules/mysql2/lib/connection.js:102:29)
    at emitOne (events.js:115:13)
    at Socket.emit (events.js:210:7)
    at addChunk (_stream_readable.js:264:12)
    at readableAddChunk (_stream_readable.js:251:11)
    at Socket.Readable.push (_stream_readable.js:209:10)
    at TCP.onread (net.js:587:20)