I just cant find a fitting solution for this MySQL “Exists()” error

Question

I already searched stackoverflow for like an hour, but no solution can solve my problem.

I want to run this code:

for (var skin in body){
  connection.query(`IF NOT EXISTS(SELECT MarketName FROM Skins WHERE MarketName = ?);
            THEN
                INSERT INTO Skins (MarketName) VALUES (?);
            END IF;`,[skin, skin]); }

But if I run this with nodejs, I get this error:

/var/www/html/bot/node_modules/mysql/lib/protocol/Parser.js:80 throw err; // Rethrow non-MySQL errors ^ 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 'IF NOT EXISTS(SELECT MarketName FROM Skins WHERE MarketName = 'Nova | Moon in Li' at line 1 at Query.Sequence._packetToError (/var/www/html/bot/node_modules/mysql/lib/protocol/sequences/Sequence.js:52:14) at Query.ErrorPacket (/var/www/html/bot/node_modules/mysql/lib/protocol/sequences/Query.js:77:18) at Protocol._parsePacket (/var/www/html/bot/node_modules/mysql/lib/protocol/Protocol.js:279:23) at Parser.write (/var/www/html/bot/node_modules/mysql/lib/protocol/Parser.js:76:12) at Protocol.write (/var/www/html/bot/node_modules/mysql/lib/protocol/Protocol.js:39:16) at Socket. (/var/www/html/bot/node_modules/mysql/lib/Connection.js:103:28) at emitOne (events.js:115:13) at Socket.emit (events.js:210:7) at addChunk (_stream_readable.js:266:12) at readableAddChunk (_stream_readable.js:253:11) -------------------- at Protocol._enqueue (/var/www/html/bot/node_modules/mysql/lib/protocol/Protocol.js:145:48) at Connection.query (/var/www/html/bot/node_modules/mysql/lib/Connection.js:208:25) at Request._callback (/var/www/html/bot/index.js:531:16) at Request.self.callback (/var/www/html/bot/node_modules/request/request.js:186:22) at emitTwo (events.js:125:13) at Request.emit (events.js:213:7) at Request. (/var/www/html/bot/node_modules/request/request.js:1163:10) at emitOne (events.js:115:13) at Request.emit (events.js:210:7) at IncomingMessage. (/var/www/html/bot/node_modules/request/request.js:1085:12)

I would appreciate your help.

Gordon Linoff Gordon Linoff · Accepted Answer · 2017-10-03T12:21:53

MySQL only allows IF statements in programming blocks -- stored procedures, triggers, and the like.

The correct way to do what you want is to create a unique index or constraint on Skins(MarketName). That way, the database ensures integrity of the data. You can do this as:

create unique index unq_skins_marketname on Skins(MarketName);

Then, an attempt to insert a duplicate will result in an error. You can generally avoid this by doing:

insert into skins(marketname)
    values (?)
    on duplicate key marketname = values(marketname);  -- this is a no-op

I just cant find a fitting solution for this MySQL “Exists()” error

1 Answers