How to concatenate two string during MySQL UPDATE query?

问题

Use case: Created a record Spot, Code, Language, Count ...later found out language entered was wrong. Tried to change the language using UPDATE query. Concatenated string still show same. Updated language string not changed in the concatenated string.

Created record using this MySql query

$sql = "INSERT INTO library (spot,code,language,count,litcode) values(?,?,?,?,CONCAT(language,'-',code))";

Tried to UPDATE language using this MySql query

Database::connect(); $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); 
$sql = "UPDATE literatures set spot = ?, code = ?,language = ?, count =?, litcode = CONCAT(language,'-',code) WHERE id = ?";
$q = $pdo->prepare($sql); 
$q->execute(array($spot,$code,$language,$count,$litcode,$id)); 
Database::disconnect();

Finally language was updated but its not updating in the concatenated string.

Any errors in the UPDATE query?

回答1:

You are trying to bind $litcode but you have CONCAT(language,'-',code). You have 5 ? in your query but you are trying to bind 6 params.

Change your code to this:

Database::connect(); 
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); 
$sql = "UPDATE literatures set spot = ?, code = ?, language = ?, count = ?, litcode = ? WHERE id = ?";
$q = $pdo->prepare($sql); 
$q->execute(array($spot,$code,$language,$count,$litcode,$id)); 
Database::disconnect();

来源：https://stackoverflow.com/questions/31668616/how-to-concatenate-two-string-during-mysql-update-query