Find good way to avoid duplicate key errors

[NullEnt1ty]

When you try to insert an already existing user (username and email are unique contraints) the database throws an error:

QueryFailedError: Duplicate entry 'my_username' for key 'IDX_78a916df40e02a9deb1c4b75ed'
    at new QueryFailedError (/home/dominique/Documents/projects/nestjs-typeorm-example/src/error/QueryFailedError.ts:9:9)
    at Query.onResult (/home/dominique/Documents/projects/nestjs-typeorm-example/src/driver/mysql/MysqlQueryRunner.ts:163:37)
    at Query.execute (/home/dominique/Documents/projects/nestjs-typeorm-example/node_modules/mysql2/lib/commands/command.js:30:14)
    at PoolConnection.handlePacket (/home/dominique/Documents/projects/nestjs-typeorm-example/node_modules/mysql2/lib/connection.js:455:32)
    at PacketParser.onPacket (/home/dominique/Documents/projects/nestjs-typeorm-example/node_modules/mysql2/lib/connection.js:73:18)
    at PacketParser.executeStart (/home/dominique/Documents/projects/nestjs-typeorm-example/node_modules/mysql2/lib/packet_parser.js:75:16)
    at Socket.<anonymous> (/home/dominique/Documents/projects/nestjs-typeorm-example/node_modules/mysql2/lib/connection.js:80:31)
    at Socket.emit (events.js:182:13)
    at Socket.EventEmitter.emit (domain.js:442:20)
    at addChunk (_stream_readable.js:283:12)

The goal ist to find a good way to avoid these errors.

• Query the database before attempting to insert the user?
• Catch the error and try to parse it (that feels shabby)?