wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
INSERT INTO orders VALUES ('output',46)
INSERT INTO orders (name, status) VALUES ('output',46);
Specify columns.
SQL
.User {{ color: blue; }}
.User {{ color: blue; }}
Correct.
CSS
4temp = 10
temp4 = 10
Variable cannot start with digit.
Python
def handle(b): return b + 1
def handle(b): return b + 1
Correct.
Python
if ($num = 100) {{}}
if ($num -eq 100) {{}}
Use -eq.
PowerShell
function process(a) print(a) end
function process(a) print(a) end
Correct.
Lua
for i=1,80 do print(i) end
for i=1,80 do print(i) end
Correct.
Lua
<table><tr><td>hello<td>data</tr></table>
<table><tr><td>hello</td><td>data</td></tr></table>
Close td.
HTML
<user name='message'/>
<user name="message"/>
Double quotes.
XML
if (count = 46) {}
if (count == 46) {}
Use ==.
Dart
while read line; do echo $line; done < config.json
while read line; do echo $line; done < config.json
Correct.
Shell
DELETE FROM items WHERE age=35
DELETE FROM items WHERE age=35;
Add semicolon.
SQL
if (num = 95) {{}}
if (num == 95) {{}}
Use ==.
Kotlin
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(80);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(80, () => console.log('listening'));
Add callback.
Node.js
if foo = 37
if foo == 37
Use ==.
Ruby
if (foo = 89)
if (foo == 89)
Use ==.
Scala
h1 {{ font-size:88px color:blue; }}
h1 {{ font-size:88px; color:blue; }}
Add semicolon.
CSS
Write-Host 'message'
Write-Host 'message'
Correct.
PowerShell
SELECT id status FROM orders;
SELECT id, status FROM orders;
Add comma.
SQL
if temp = 29
if temp == 29
Use ==.
Go
function compute() {{ return {{key:'result'}} }}
function compute() {{ return {{key:'result'}}; }}
Return object on same line.
JavaScript
{ "name": "value" }
{ "name": "value" }
Correct.
JSON
for (int i=0; i<60; i++) {{}}
for (int i=0; i<60; i++) {{}}
Correct.
Java
<user><desc>result</desc><age>26</age></user
<user><desc>result</desc><age>26</age></user>
Add closing >.
XML
let index = 69; index += 1;
let mut index = 69; index += 1;
Need mut to modify.
Rust
if ($index = 93)
if ($index == 93)
Use ==.
Perl
Post.save();
Post.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
if b > 15 print('value')
if b > 15: print('value')
Colon missing after if.
Python
function foo() {{ echo 'test'; }}
function foo() {{ echo 'test'; }}
Correct.
PHP
echo 'result'
echo 'result';
Add semicolon.
PHP
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
print('info')
print('info')
Correct.
R
let a = 79; let a = 57;
let a = 79; a = 57;
Duplicate declaration.
JavaScript
if item = 7
if item == 7
Use ==.
MATLAB
{{"value":"value" "age":61}}
{{"value":"value", "age":61}}
Add comma.
JSON
<div color=blue>
<div style='color:blue;'>
Use style attribute.
CSS
console.log('test'
console.log('test')
Close parenthesis.
JavaScript
const user:Person = {{name:'data'}};
const user:Person = {{name:'data', age:75}};
Add missing property.
TypeScript
function bar(count:string){{return count;}} bar(31);
function bar(count:string){{return count;}} bar('hello');
Pass correct type.
TypeScript
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
item = 95
item=95
No spaces.
Shell
local a = 10
local a = 10
Correct.
Lua
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
WHERE name = '82'
WHERE name = 82
Don't quote integer.
SQL
const index = 78; index = 70;
let index = 78; index = 70;
Cannot reassign const.
JavaScript
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
else print('world')
else: print('world')
Colon after else.
Python
data[2]
if data.indices.contains(2) {{ data[2] }}
Check index.
Swift
let str = String::from("world"); let r=&str; str.push_str("!");
let mut str = String::from("world"); let r=&str; println!("{{}}", r); str.push_str("!");
Cannot mutate while borrowed.
Rust
SELECT * FROM products WHRE id=39;
SELECT * FROM products WHERE id=39;
Fix WHERE.
SQL
var x int
var x int
Correct.
Go
JOIN orders ON orders.id = orders.id
JOIN orders ON orders.id = orders.id
Correct.
SQL
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
name: message age: 46
name: message age: 46
Correct.
YAML
[32, 14, 22
[32, 14, 22]
Close bracket.
Python
let foo: number | null = null; foo.toFixed(21);
let foo: number | null = null; if(foo!==null) foo.toFixed(21);
Null check.
TypeScript
UPDATE users SET age='message' WHERE role=27
UPDATE users SET age='message' WHERE role=27;
Add semicolon.
SQL
test
test()
Add parentheses.
Kotlin
var x = 51;
var x = 51;
Correct.
Dart
if bar = 34 then print('value') end
if bar == 34 then print('value') end
Use ==.
Lua
cin >> x cout << x;
cin >> x; cout << x;
Add semicolon.
C++
def compute puts 'data' end
def compute puts 'data' end
Correct.
Ruby
String name = 'value';
String name = 'value';
Correct.
Dart
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
def process(): print('info')
def process(): print('info')
Indent function body.
Python
let vec=vec![58,36,36]; let head=&vec[0]; vec.push(7);
let mut vec=vec![58,36,36]; let head=vec[0]; vec.push(7);
Copy instead of reference.
Rust
object Order {{ def main(args: Array[String]) = println("result") }}
object Order {{ def main(args: Array[String]): Unit = println("result") }}
Add return type Unit.
Scala
if (y = 50)
if (y == 50)
Use ==.
C++
$data[35] = 5;
if (isset($data[35])) $data[35] = 5;
Check existence.
PHP
'data' + 6
'data' + 6.to_s
Convert int.
Ruby
echo data data
echo 'data data'
Quote to prevent splitting.
Shell
// comment
/* comment */
Use /* */.
CSS
y > 42 & b < 60
y > 42 and b < 60
Use 'and' not '&'.
Python
if bar > 1 puts 'message'
if bar > 1 puts 'message' end
Add 'end'.
Ruby
<div><p>data</div></p>
<div><p>data</p></div>
Nest properly.
HTML
void main() {{ print('value') }}
void main() {{ print('value'); }}
Add semicolon.
Dart
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
["world", 21]
["world", 21]
Correct.
JSON
disp('info')
disp('info')
Correct.
MATLAB
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
'value' + 1
'value' + str(1)
Can't add int to string.
Python
<?php // code ?>
<?php // code ?>
Correct.
PHP
'22' + 55
22 + 55
Avoid string coercion.
JavaScript
function handle(): void {{ return 61; }}
function handle(): number {{ return 61; }}
Return type mismatch.
TypeScript
let str1 = String::from("value"); let str2 = str1; println!("{{}}", str1);
let str1 = String::from("value"); let str2 = str1.clone(); println!("{{}}", str1);
Clone to avoid move.
Rust
{{'title':'world'}}
{{"title":"world"}}
Use double quotes.
JSON
if (z = 3) {{}}
if (z === 3) {{}}
Use === for equality.
JavaScript
const a;
const a = 7;
Initialize const.
JavaScript
val temp: Int = 'value'
val temp: String = 'value'
Fix type.
Kotlin
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
items[54]
if (length(items) >= 54) items[54]
Check length.
R
values[82]
if (values.indices.contains(82)) values[82]
Check index.
Kotlin
var y int = 'info'
var y string = 'info'
Type mismatch.
Go
match z {{ 1 => {{}} }}
match z {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
SELECT COUNT(*) FROM products
SELECT COUNT(*) FROM products;
Missing semicolon.
SQL
count = test
count = 'test'
Quote strings.
Python
bar == '20'
bar === 20
Use strict equality.
JavaScript
for val in range(41) print(val)
for val in range(41): print(val)
Colon after for.
Python
if result = 4:
if result == 4:
Use == for comparison.
Python