Environment

Knex version: 0.16.3 Database + version: mysql Ver 14.14 Distrib 5.7.25, for Linux (x86_64) using EditLine wrapper OS: Debian buster

Bug

1. Explain what kind of behaviour you are getting and how you think it should do

Using .raw with an escaped question mark ('\\?') and other methods (limit, where, …), database server returns a syntax error

1. Error message

Unhandled rejection Error: ER_PARSE_ERROR: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '?' at line 1
    at Query.Sequence._packetToError (/home/urungi/urungi/node_modules/mysql/lib/protocol/sequences/Sequence.js:47:14)
    at Query.ErrorPacket (/home/urungi/urungi/node_modules/mysql/lib/protocol/sequences/Query.js:77:18)
    at Protocol._parsePacket (/home/urungi/urungi/node_modules/mysql/lib/protocol/Protocol.js:278:23)
    at Parser.write (/home/urungi/urungi/node_modules/mysql/lib/protocol/Parser.js:76:12)
    at Protocol.write (/home/urungi/urungi/node_modules/mysql/lib/protocol/Protocol.js:38:16)
    at Socket.<anonymous> (/home/urungi/urungi/node_modules/mysql/lib/Connection.js:91:28)
    at Socket.<anonymous> (/home/urungi/urungi/node_modules/mysql/lib/Connection.js:502:10)
    at emitOne (events.js:116:13)
    at Socket.emit (events.js:211:7)
    at addChunk (_stream_readable.js:263:12)
    at readableAddChunk (_stream_readable.js:250:11)
    at Socket.Readable.push (_stream_readable.js:208:10)
    at TCP.onread (net.js:607:20)
    --------------------
    at Protocol._enqueue (/home/urungi/urungi/node_modules/mysql/lib/protocol/Protocol.js:144:48)
    at Connection.query (/home/urungi/urungi/node_modules/mysql/lib/Connection.js:200:25)
    at /home/urungi/urungi/node_modules/knex/lib/dialects/mysql/index.js:144:18
    at Promise._execute (/home/urungi/urungi/node_modules/knex/node_modules/bluebird/js/release/debuggability.js:313:9)
    at Promise._resolveFromExecutor (/home/urungi/urungi/node_modules/knex/node_modules/bluebird/js/release/promise.js:483:18)
    at new Promise (/home/urungi/urungi/node_modules/knex/node_modules/bluebird/js/release/promise.js:79:10)
    at Client_MySQL._query (/home/urungi/urungi/node_modules/knex/lib/dialects/mysql/index.js:135:12)
    at Client_MySQL.query (/home/urungi/urungi/node_modules/knex/lib/client.js:192:17)
    at Runner.<anonymous> (/home/urungi/urungi/node_modules/knex/lib/runner.js:138:36)
    at Runner.tryCatcher (/home/urungi/urungi/node_modules/knex/node_modules/bluebird/js/release/util.js:16:23)
    at Runner.query (/home/urungi/urungi/node_modules/knex/node_modules/bluebird/js/release/method.js:15:34)
    at /home/urungi/urungi/node_modules/knex/lib/runner.js:47:21
    at tryCatcher (/home/urungi/urungi/node_modules/knex/node_modules/bluebird/js/release/util.js:16:23)
    at /home/urungi/urungi/node_modules/knex/node_modules/bluebird/js/release/using.js:185:26
    at tryCatcher (/home/urungi/urungi/node_modules/knex/node_modules/bluebird/js/release/util.js:16:23)
    at Promise._settlePromiseFromHandler (/home/urungi/urungi/node_modules/knex/node_modules/bluebird/js/release/promise.js:512:31)

1. Reduced test code

const knex = require('knex')({
    client: 'mysql',
    connection: {
        host: '127.0.0.1',
        user: 'user',
        password: 'user',
        database: 'koha'
    }
});

const qb = knex('borrowers')
    .select(knex.raw('CONCAT(??, "\\?")', 'borrowernumber'))
    .limit(1);

console.log(qb.toString());
// select CONCAT(`borrowernumber`, "?") from `borrowers` limit 1
// This query, if executed manually in mysql client, is valid and returns results

qb.then(result => {
    console.log(result);  // This is never executed
});