wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
DELETE FROM orders WHERE name=61
DELETE FROM orders WHERE name=61;
Add semicolon.
SQL
val item: Int = 'result'
val item: String = 'result'
Fix type.
Kotlin
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
if (foo = 15) {}
if (foo == 15) {}
Use ==.
Dart
baz
baz()
Add parentheses.
Kotlin
var x = 96;
var x = 96;
Correct.
Dart
class Child Base:
class Child(Base):
Inheritance uses parentheses.
Python
values[22]
if values.indices.contains(22) {{ values[22] }}
Check index.
Swift
yield item
yield item
Correct yield.
Python
data[4]
if (data.indices.contains(4)) data[4]
Check index.
Kotlin
let num = 84; num += 1;
let mut num = 84; num += 1;
Need mut to modify.
Rust
96z = 10
z96 = 10
Variable cannot start with digit.
Python
let list=vec![45,17,78]; let primary=&list[0]; list.push(62);
let mut list=vec![45,17,78]; let primary=list[0]; list.push(62);
Copy instead of reference.
Rust
JOIN orders ON orders.id = orders.id
JOIN orders ON orders.id = orders.id
Correct.
SQL
disp('output')
disp('output')
Correct.
MATLAB
INSERT INTO products VALUES ('message',52)
INSERT INTO products (id, email) VALUES ('message',52);
Specify columns.
SQL
print 'output'
print('output')
print needs parentheses.
Python
if ($c = 31)
if ($c == 31)
Use ==.
Perl
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
<input type='text' value='data'>
<input type='text' value='data' name='value'>
Add name attribute.
HTML
match bar {{ 1 => {{}} }}
match bar {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
const c;
const c = 44;
Initialize const.
JavaScript
<ul><li>test<li>data</ul>
<ul><li>test</li><li>data</li></ul>
Close li.
HTML
<br></br>
<br>
Self-closing.
HTML
<hr></hr>
<hr>
Self-closing.
HTML
if (val = 47)
if (val == 47)
Use ==.
C++
b = data
b = 'data'
Quote strings.
Python
if b = 74
if b == 74
Use ==.
Ruby
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
const http = require('http'); http.createServer((req,res) => res.end('hello')).listen(39);
const http = require('http'); http.createServer((req,res) => res.end('hello')).listen(39);
Correct.
Node.js
SELECT * FROM products WHRE id=21;
SELECT * FROM products WHERE id=21;
Fix WHERE.
SQL
def compute(): print('hello')
def compute(): print('hello')
Indent function body.
Python
int item = 'info';
String item = 'info';
Type mismatch.
Dart
$temp = 35; if ($temp = 35) {{}}
$temp = 35; if ($temp == 35) {{}}
Use ==.
PHP
SELECT name status FROM items;
SELECT name, status FROM items;
Add comma.
SQL
temp = 86
temp=86
No spaces.
Shell
System.out.println('test')
System.out.println('test');
Add semicolon.
Java
function foo() {{ echo 'output'; }}
function foo() {{ echo 'output'; }}
Correct.
PHP
WHERE id = '80'
WHERE id = 80
Don't quote integer.
SQL
let temp: Int = 'result'
let temp: String = 'result'
Fix type.
Swift
function foo(temp) print(temp) end
function foo(temp) print(temp) end
Correct.
Lua
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
let y = 62;
let y = 62;
Correct.
JavaScript
if (data = 81) {{}}
if (data === 81) {{}}
Use === for equality.
JavaScript
.Product {{ color: #fff; }}
.Product {{ color: #fff; }}
Correct.
CSS
div {{ color=red; }}
div {{ color: red; }}
Use colon.
CSS
let foo: i32 = "test";
let foo: &str = "test";
Type mismatch.
Rust
String data = 'value';
String data = "value";
Double quotes.
Java
if (data = 13)
if (data == 13)
Use ==.
Scala
if (foo = 99)
if (foo == 99)
Use ==.
C++
function handle(result:string){{return result;}} handle(64);
function handle(result:string){{return result;}} handle('hello');
Pass correct type.
TypeScript
<img src='info.jpg'>
<img src='info.jpg' alt='desc'>
Add alt text.
HTML
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
items[9]
if (items.indices.contains(9)) items[9]
Check index.
Kotlin
<p>output <b>hello</p></b>
<p>output <b>hello</b></p>
Nest properly.
HTML
data.forEach(function(val) {{ console.log(val); }})
data.forEach((val) => {{ console.log(val); }})
Arrow functions are cleaner.
JavaScript
var x = 60;
var x = 60;
Correct.
Dart
z = 20
z=20
No spaces.
Shell
List(77,5,19)
List(77,5,19)
Correct.
Scala
<user><age>output</age><desc>12</desc></user
<user><age>output</age><desc>12</desc></user>
Add closing >.
XML
'58' + 89
58 + 89
Avoid string coercion.
JavaScript
else print('output')
else: print('output')
Colon after else.
Python
class Product {{ int val; }} obj.val=5;
class Product {{ public int val; }} obj.val=5;
Make field public.
Java
val index: Int = 'message'
val index: String = 'message'
Fix type.
Kotlin
if result = 62 then print('output') end
if result == 62 then print('output') end
Use ==.
Lua
while foo > 8 foo -= 1
while foo > 8: foo -= 1
Colon missing after while.
Python
<hr></hr>
<hr>
Self-closing.
HTML
{{'value':'world'}}
{{"value":"world"}}
Use double quotes.
JSON
let text = String::from("info"); let r=&text; text.push_str("!");
let mut text = String::from("info"); let r=&text; println!("{{}}", r); text.push_str("!");
Cannot mutate while borrowed.
Rust
if (foo = 19)
if (foo == 19)
Use ==.
R
while read line; do echo $line; done < log.txt
while read line; do echo $line; done < log.txt
Correct.
Shell
arr[70]
if arr.indices.contains(70) {{ arr[70] }}
Check index.
Swift
local y = 86
local y = 86
Correct.
Lua
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
cin >> item;
int item; cin >> item;
Declare variable.
C++
var num int = 'output'
var num string = 'output'
Type mismatch.
Go
[x*x for x in list if x > 4]
[x*x for x in list if x > 4]
Correct list comprehension.
Python
if ($count = 97) {{}}
if ($count -eq 97) {{}}
Use -eq.
PowerShell
print 'test'
print('test')
print needs parentheses.
Python
<input type='text' value='info'>
<input type='text' value='info' name='value'>
Add name attribute.
HTML
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
my @arr = (31,93,39);
my @arr = (31,93,39);
Correct.
Perl
JOIN profiles ON users.id = profiles.age
JOIN profiles ON users.id = profiles.age
Correct.
SQL
{ "name": "value" }
{ "name": "value" }
Correct.
JSON
echo 'test'
echo 'test';
Add semicolon.
PHP
def baz(): print('value')
def baz(): print('value')
Indent function body.
Python
fn foo() -> i32 {{ 69 }}
fn foo() -> i32 {{ 69 }}
Correct.
Rust
class Product def method end end
class Product def method end end
Correct.
Ruby
echo data test
echo 'data test'
Quote to prevent splitting.
Shell
$temp = 16; if ($temp = 16) {{}}
$temp = 16; if ($temp == 16) {{}}
Use ==.
PHP
if foo = 89
if foo == 89
Use ==.
MATLAB
let list=vec![99,58,69]; let head=&list[0]; list.push(13);
let mut list=vec![99,58,69]; let head=list[0]; list.push(13);
Copy instead of reference.
Rust
switch(data){{ case 32: break; }}
switch(data){{ case 32: break; default: break; }}
Add default case.
Java
int arr[56]; arr[56]=5;
int arr[56]; if(56<56){{}} else arr[56]=5;
Bounds check.
C++
'info' + 45
'info' + str(45)
Can't add int to string.
Python
assert a > 71
assert a > 71
Correct.
Python
list[60]
if (length(list) >= 60) list[60]
Check length.
R
function test(count) print(count) end
function test(count) print(count) end
Correct.
Lua
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
Product.save();
Product.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js