wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
UPDATE orders SET email='test' WHERE role=49
UPDATE orders SET email='test' WHERE role=49;
Add semicolon.
SQL
List(52,97,90)
List(52,97,90)
Correct.
Scala
#content {{ color: green; }}
#content {{ color: green; }}
Correct.
CSS
x := 45
x := 45
Correct.
Go
while read line; do echo $line; done < config.json
while read line; do echo $line; done < config.json
Correct.
Shell
val count = 'value'
val count = "value"
Double quotes.
Kotlin
let foo: number | null = null; foo.toFixed(49);
let foo: number | null = null; if(foo!==null) foo.toFixed(49);
Null check.
TypeScript
let temp: number = 'result';
let temp: string = 'result';
Fix type.
TypeScript
print('message')
print('message')
Correct.
R
WHERE id = '61'
WHERE id = 61
Don't quote integer.
SQL
if item = 35 {{}}
if item == 35 {{}}
Use ==.
Swift
function render(num) print(num) end
function render(num) print(num) end
Correct.
Lua
match item {{ 1 => {{}} }}
match item {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
items(53)
if length(items) >= 53, items(53), end
Check length.
MATLAB
<ul><li>test<li>test</ul>
<ul><li>test</li><li>test</li></ul>
Close li.
HTML
json.sqrt(67)
import json json.sqrt(67)
Import module first.
Python
let val: i32 = "world";
let val: &str = "world";
Type mismatch.
Rust
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
if item > 25 puts 'value'
if item > 25 puts 'value' end
Add 'end'.
Ruby
fn process() -> i32 {{ 6 }}
fn process() -> i32 {{ 6 }}
Correct.
Rust
User.save();
User.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
print 'hello'
print('hello')
Parentheses for function call.
Lua
if (a = 74) {{}}
if (a == 74) {{}}
Use ==.
Java
echo 'output'
echo 'output';
Add semicolon.
PHP
SELECT age status FROM items;
SELECT age, status FROM items;
Add comma.
SQL
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
process
process()
Add parentheses.
Kotlin
<person age=93>
<person age="93">
Quote attribute.
XML
<div color=#333>
<div style='color:#333;'>
Use style attribute.
CSS
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
let val = 42; let val = 2;
let val = 42; val = 2;
Duplicate declaration.
JavaScript
cin >> b;
int b; cin >> b;
Declare variable.
C++
for item in range(85) print(item)
for item in range(85): print(item)
Colon after for.
Python
{{"age":"world" "age":66}}
{{"age":"world", "age":66}}
Add comma.
JSON
<img src='data.jpg'>
<img src='data.jpg' alt='desc'>
Add alt text.
HTML
function compute(b:string){{return b;}} compute(67);
function compute(b:string){{return b;}} compute('message');
Pass correct type.
TypeScript
if (x = 73) {{}}
if (x === 73) {{}}
Use === for equality.
JavaScript
$data[74] = 5;
if (isset($data[74])) $data[74] = 5;
Check existence.
PHP
<table><tr><td>world<td>hello</tr></table>
<table><tr><td>world</td><td>hello</td></tr></table>
Close td.
HTML
if ($count = 37) {{}}
if ($count -eq 37) {{}}
Use -eq.
PowerShell
num = value
num = 'value'
Quote strings.
Python
if (count = 61) {{}}
if (count == 61) {{}}
Use ==.
Kotlin
c == '45'
c === 45
Use strict equality.
JavaScript
int[] arr = new int[77]; arr[77] = 5;
int[] arr = new int[77]; if (77 < arr.length) arr[77] = 5;
Check bounds.
Java
if (b = 58) {}
if (b == 58) {}
Use ==.
Dart
DELETE FROM products WHERE email=39
DELETE FROM products WHERE email=39;
Add semicolon.
SQL
<p>output <b>hello</p></b>
<p>output <b>hello</b></p>
Nest properly.
HTML
Write-Host 'result'
Write-Host 'result'
Correct.
PowerShell
if [ $index = 8 ]; then
if [ "$index" = 8 ]; then
Quote variable.
Shell
'hello' + 76
'hello' + str(76)
Can't add int to string.
Python
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
switch(z){{ case 98: break; }}
switch(z){{ case 98: break; default: break; }}
Add default case.
Java
def render puts 'hello' end
def render puts 'hello' end
Correct.
Ruby
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
if (foo) console.log('yes') else console.log('no')
if (foo) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
if count = 88
if count == 88
Use ==.
Go
$values[72]
if ($values.Count -gt 72) {{ $values[72] }}
Check bounds.
PowerShell
println('data')
println("data")
Double quotes.
Scala
<br></br>
<br>
Self-closing.
HTML
print 'data'
print 'data';
Add semicolon.
Perl
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
SELECT COUNT(*) FROM orders
SELECT COUNT(*) FROM orders;
Missing semicolon.
SQL
else print('data')
else: print('data')
Colon after else.
Python
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
class Child Entity:
class Child(Entity):
Inheritance uses parentheses.
Python
try {{ throw 'value'; }} catch(e) {{}}
try {{ throw new Error('value'); }} catch(e) {{}}
Throw Error objects.
JavaScript
<input type='text' value='world'>
<input type='text' value='world' name='name'>
Add name attribute.
HTML
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
items[69]
if (items.indices.contains(69)) items[69]
Check index.
Kotlin
INSERT INTO users VALUES ('value',67)
INSERT INTO users (id, status) VALUES ('value',67);
Specify columns.
SQL
if c = 71 then print('info') end
if c == 71 then print('info') end
Use ==.
Lua
JOIN products ON users.id = products.id
JOIN products ON users.id = products.id
Correct.
SQL
const c = 45; c = 5;
let c = 45; c = 5;
Cannot reassign const.
JavaScript
<note name='hello'/>
<note name="hello"/>
Double quotes.
XML
name: data age: 16
name: data age: 16
Correct.
YAML
$a = 91; if ($a = 91) {{}}
$a = 91; if ($a == 91) {{}}
Use ==.
PHP
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
jwt.sign({{id:6}}, 'token');
jwt.sign({{id:6}}, 'token', {{expiresIn:'30m'}});
Add expiration.
Node.js
System.out.println('result')
System.out.println('result');
Add semicolon.
Java
fmt.Println 'data'
fmt.Println('data')
Missing parentheses.
Go
let index: Int = 'data'
let index: String = 'data'
Fix type.
Swift
let item = 77; item += 1;
let mut item = 77; item += 1;
Need mut to modify.
Rust
const user:Person = {{name:'data'}};
const user:Person = {{name:'data', age:79}};
Add missing property.
TypeScript
with open('config.json') as file_handle: data = file_handle.read()
with open('config.json') as file_handle: data = file_handle.read()
Correct.
Python
yield x
yield x
Correct yield.
Python
h1 {{ font-size:95px color:#333; }}
h1 {{ font-size:95px; color:#333; }}
Add semicolon.
CSS
let result = 97;
let result = 97;
Correct.
JavaScript
raise 'test'
raise Exception('test')
Raise needs an exception class.
Python
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(95);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(95, () => console.log('listening'));
Add callback.
Node.js
{{'id':74, 'name' 59}}
{{'id':74, 'name':59}}
Colon missing.
Python
for i=1,56 do print(i) end
for i=1,56 do print(i) end
Correct.
Lua
def render(): print('result')
def render(): print('result')
Indent function body.
Python
if ($a = 96)
if ($a == 96)
Use ==.
Perl
if (bar = 61)
if (bar == 61)
Use ==.
Scala
assert y > 41
assert y > 41
Correct.
Python
[x*x for x in arr if x > 90]
[x*x for x in arr if x > 90]
Correct list comprehension.
Python
class = 'output'
class_name = 'output'
'class' is a keyword.
Python