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Нашёл 3 млн ответов for 'textbook advertising UNION ALL SELECT NULL,NULL,NULL-- tyDn'.

064-29: Creating Efficient SQL - Union Join without the Union Clause
data _null_; merge a b; by key; run; KEY ACOL BCOL p one six q two seven r three eight. The row-wise join returns a single column 'col' instead with a result set containing all the rows of both constituent tables a and b, regardless of the values of each table's 'key' column. SELECT col FROM a UNION...

https://support.sas.com/resources/papers/proceedings/proceedings/sugi29/064-29.pdf

Chapter 3 Pointer Subterfuge
l One can use NULL byte attack. %00’ UNION SELECT password FROM tblUsers WHERE username=‘admin’--. URL Encoding for NULL. NULL byte can terminate strings and hence the remaining may Not be filtered May work in Managed Code Context.

https://index-of.es/Attacks/SQL%20injection%20attacks/Lecture8.pdf

Microsoft Word - Blindfolded SQL Injection - Final.doc
Injecting 11223344) UNION SELECT NULL,NULL,NULL,NULL WHERE 1=2 --, results in the following query Once the NULL-based UNION statement works, it is a trivial process to identify the types of each column. In each iteration a single field is tested for its type.

https://index-of.es/Hacking/SQL-Injection/Blindfolded_SQL_Injection.pdf

Querying Microsoft | Module 8: Querying Full-Text Indexes
Use the IS NULL search condition to retrieve rows in which information is missing from a specified column. When you retrieve rows that contain unknown values, consider the following facts and guidelines: ! Null values fail all comparisons because they do not evaluate equally with one another.

https://index-of.es/Rdbms/MSSQL%20-%20Querying%20Microsoft%20SQL%20Server%202000%20with%20Transact-SQL.pdf

Nulls Make Things Easier?
SELECT NULL < NULL + 1; ?column? -(null). NULL represents unknown, not applicable, or unassigned. It has no data type, so comparing it to xed values always returns s. WITH ordertest AS ( SELECT NULL UNION ALL SELECT 2 UNION ALL SELECT 1 UNION ALL SELECT NULL.

https://momjian.us/main/writings/pgsql/nulls.pdf

SQL Injection
1234' or 1=1 union select null from balances; -- The used SELECT statements have a different number of columns. Remediation – Prepared Statements. • Java. PreparedStatement getSales = null; String getPSstring = "select name, value from tbl1 where cond=? and status=?"

https://www.cs.montana.edu/courses/csci476/topics/sql_injection.pdf

Handling Missing Values in the SQL Procedure
IS [NOT] NULL and IS [NOT] MISSING predicates are two predicates especially designed to deal with missing values. IS [NOT] NULL is a SQL standard predicate and IS [NOT] MISSING is SAS SQL predicate. They are generic because they can handle both numeric and character variables.

https://stats.idre.ucla.edu/wp-content/uploads/2016/02/p004.pdf

iqapgv2.book
This row contains NULL in both the Year and Quarter columns and is the row where all columns were excluded from the prefix. Note Every ROLLUP operation returns a result set with one row where NULL appears in each column except for the aggregate column. This row represents the summary of each...

http://infocenter.sybase.com/help/topic/com.sybase.infocenter.dc00800.1510/pdf/iqapgv2.pdf

commands.book
• NULL – removes the binding to the current template database. The database uses model as its template database during subsequent server restarts. • Non-null values – if there is a referenced row where each corresponding column is equal in the referenced table, then the referential integrity...

http://infocenter.sybase.com/help/topic/com.sybase.infocenter.dc36272.1550/pdf/commands.pdf

sqlug.book
The basic query operations in a relational system are selection (also called restriction), projection, and join. These can all be combined in the SQL select command. A selection is a subset of the rows in a table.

http://infocenter.sybase.com/help/topic/com.sybase.infocenter.dc32300.1570/pdf/sqlug.pdf