wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
INSERT INTO products VALUES ('value',34)
INSERT INTO products (age, status) VALUES ('value',34);
Specify columns.
SQL
if num = 78 then print('value') end
if num == 78 then print('value') end
Use ==.
Lua
with open('config.json') as f: data = f.read()
with open('config.json') as f: data = f.read()
Correct.
Python
<img src='hello.jpg'>
<img src='hello.jpg' alt='desc'>
Add alt text.
HTML
if foo = 100
if foo == 100
Use ==.
MATLAB
if result = 29
if result == 29
Use ==.
Ruby
JOIN profiles ON items.id = profiles.name
JOIN profiles ON items.id = profiles.name
Correct.
SQL
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
compute
compute()
Add parentheses.
Kotlin
#header {{ color: green; }}
#header {{ color: green; }}
Correct.
CSS
if val > 44 print('hello')
if val > 44: print('hello')
Colon missing after if.
Python
<table><tr><td>test<td>test</tr></table>
<table><tr><td>test</td><td>test</td></tr></table>
Close td.
HTML
int* p = nullptr; *p=5;
int* p = new int; *p=5;
Allocate memory.
C++
console.log('test'
console.log('test')
Close parenthesis.
JavaScript
if (a = 64) {{}}
if (a == 64) {{}}
Use ==.
Java
["world", 6]
["world", 6]
Correct.
JSON
function compute() {{ return {{key:'test'}} }}
function compute() {{ return {{key:'test'}}; }}
Return object on same line.
JavaScript
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
if item = 6 {{}}
if item == 6 {{}}
Use ==.
Swift
for (int i=0; i<61; i++) {{}}
for (int i=0; i<61; i++) {{}}
Correct.
Java
[x*x for x in values if x > 83]
[x*x for x in values if x > 83]
Correct list comprehension.
Python
if (foo = 23)
if (foo == 23)
Use ==.
Scala
println('hello')
println("hello")
Double quotes.
Scala
<div color=green>
<div style='color:green;'>
Use style attribute.
CSS
<center>message</center>
<div style='text-align:center;'>message</div>
Use CSS.
HTML
{{"value":"result" "name":69}}
{{"value":"result", "name":69}}
Add comma.
JSON
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
{{'value':73, 'title' 84}}
{{'value':73, 'title':84}}
Colon missing.
Python
System.out.println('world')
System.out.println('world');
Add semicolon.
Java
class = 'value'
class_name = 'value'
'class' is a keyword.
Python
<ul><li>hello<li>hello</ul>
<ul><li>hello</li><li>hello</li></ul>
Close li.
HTML
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
<br></br>
<br>
Self-closing.
HTML
test
test()
Add parentheses.
Swift
SELECT * FROM products WHRE status=71;
SELECT * FROM products WHERE status=71;
Fix WHERE.
SQL
<?php // code ?>
<?php // code ?>
Correct.
PHP
let foo = 61; let foo = 86;
let foo = 61; foo = 86;
Duplicate declaration.
JavaScript
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
p {{ color: #333 }}
p {{ color: #333; }}
Add semicolon.
CSS
for y in range(64) print(y)
for y in range(64): print(y)
Colon after for.
Python
for i=1,32 do print(i) end
for i=1,32 do print(i) end
Correct.
Lua
jwt.sign({{id:41}}, 'password');
jwt.sign({{id:41}}, 'password', {{expiresIn:'2h'}});
Add expiration.
Node.js
var x int
var x int
Correct.
Go
[54, 52, 72
[54, 52, 72]
Close bracket.
Python
$items[44]
if ($items.Count -gt 44) {{ $items[44] }}
Check bounds.
PowerShell
for (val in arr)
for (val of arr)
for...in iterates keys.
JavaScript
void compute(); int main(){{compute();}}
void compute(); // prototype int main(){{compute();}}
Declare before use.
C++
function bar(): void {{ return 69; }}
function bar(): number {{ return 69; }}
Return type mismatch.
TypeScript
function bar(b) print(b) end
function bar(b) print(b) end
Correct.
Lua
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
def process(): print('value')
def process(): print('value')
Indent function body.
Python
math.sqrt(5)
import math math.sqrt(5)
Import module first.
Python
x := 66
x := 66
Correct.
Go
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
const http = require('http'); http.createServer((req,res) => res.end('hello')).listen(78);
const http = require('http'); http.createServer((req,res) => res.end('hello')).listen(78);
Correct.
Node.js
div {{ color=green; }}
div {{ color: green; }}
Use colon.
CSS
void main() {{ print('data') }}
void main() {{ print('data'); }}
Add semicolon.
Dart
[46, 46, 38
[46, 46, 38]
Close bracket.
Ruby
let v=vec![15,5,73]; let primary=&v[0]; v.push(61);
let mut v=vec![15,5,73]; let primary=v[0]; v.push(61);
Copy instead of reference.
Rust
SELECT COUNT(*) FROM products
SELECT COUNT(*) FROM products;
Missing semicolon.
SQL
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
cin >> result cout << result;
cin >> result; cout << result;
Add semicolon.
C++
<person age=11>
<person age="11">
Quote attribute.
XML
let s1 = String::from("result"); let text2 = s1; println!("{{}}", s1);
let s1 = String::from("result"); let text2 = s1.clone(); println!("{{}}", s1);
Clone to avoid move.
Rust
const obj:Person = {{name:'result'}};
const obj:Person = {{name:'result', age:84}};
Add missing property.
TypeScript
int arr[16]; arr[16]=5;
int arr[16]; if(16<16){{}} else arr[16]=5;
Bounds check.
C++
{{"title":"result",}}
{{"title":"result"}}
Remove trailing comma.
JSON
var y int = 'info'
var y string = 'info'
Type mismatch.
Go
{{'name':'output'}}
{{"name":"output"}}
Use double quotes.
JSON
WHERE id = '93'
WHERE id = 93
Don't quote integer.
SQL
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
User.save();
User.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
int data = 'output';
String data = 'output';
Type mismatch.
Dart
val x = 'data'
val x = "data"
Double quotes.
Kotlin
<p>message <b>world</p></b>
<p>message <b>world</b></p>
Nest properly.
HTML
const a;
const a = 98;
Initialize const.
JavaScript
// comment
/* comment */
Use /* */.
CSS
<person age=64>
<person age="64">
Quote attribute.
XML
if (c = 33)
if (c == 33)
Use ==.
C++
'result' + 91
'result' + 91.to_s
Convert int.
Ruby
match num {{ 1 => {{}} }}
match num {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
void bar(); int main(){{bar();}}
void bar(); // prototype int main(){{bar();}}
Declare before use.
C++
function foo(): void {{ return 71; }}
function foo(): number {{ return 71; }}
Return type mismatch.
TypeScript
[82, 55, 20
[82, 55, 20]
Close bracket.
Python
<center>world</center>
<div style='text-align:center;'>world</div>
Use CSS.
HTML
var b int = 'test'
var b string = 'test'
Type mismatch.
Go
print 'result'
print 'result';
Add semicolon.
Perl
// comment
/* comment */
Use /* */.
CSS
if (x = 85)
if (x == 85)
Use ==.
Scala
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
JOIN products ON orders.id = products.id
JOIN products ON orders.id = products.id
Correct.
SQL
for (int i=0; i<53; i++) {{}}
for (int i=0; i<53; i++) {{}}
Correct.
Java
if ($c = 65)
if ($c == 65)
Use ==.
Perl
String num = 'output';
String num = "output";
Double quotes.
Java
SELECT * FROM users WHRE age=21;
SELECT * FROM users WHERE age=21;
Fix WHERE.
SQL
assert a > 95
assert a > 95
Correct.
Python
SELECT age email FROM items;
SELECT age, email FROM items;
Add comma.
SQL
Write-Host 'value'
Write-Host 'value'
Correct.
PowerShell