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sql - Union to handle NULL values - Stack Overflow

stackoverflow.com

select a,b,null,null from table1 union select null,null,c,d from table2 union select null,null,null,null,e,f from table3.

sql - CONCAT'ing NULL fields - Stack Overflow | Post as a guest

stackoverflow.com

I have a table with three fields, FirstName, LastName and Email. Here's some dummy data: … Now, if I do: … Vitals for Joe is null, as there is a single null field. How do you overcome this behaviour?

mysql - Site has been hacked via SQL Injection - Stack Overflow

stackoverflow.com

0x31303235343830303536 is NULL - they are just matching the number of columns in your existing query. If you had SELECT * FROM users and users had 4 columns, the UNION must also have 4 columns. As a result, they just used `NULL values to populate those columns.

SQL is null and = null - Stack Overflow

stackoverflow.com

What is the difference between … and … and why does the latter not work?

SQL NULL Values - IS NULL and IS NOT NULL

www.w3schools.com

Note: A NULL value is different from a zero value or a field that contains spaces.

php - A customers site had a big mysql injection attack on it, just want...

security.stackexchange.com

union all select null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null

SQL-Injection-Payloads/sqli-misc.txt at master...

github.com

-999.9+union+all+select+%27R3DM0V3_hvj_injection',null%2CNULL%2CNULL%2CNULL%2CNULL%2CNULL

Заметка про NULL / Хабр

habr.com

Даже выражение NULL != NULL не будет истинным, ведь нельзя однозначно сравнить одну неизвестность с другой. Кстати, ложным это выражение тоже не будет, потому что при вычислении условий Oracle не ограничивается состояниями ИСТИНА и ЛОЖЬ.

Modern SQL: NULL — purpose, comparisons, NULL in expressions...

modern-sql.com

SQL’s NULL indicates absent data. NULL propagates through expressions and needs distinct comparison operators.

Null (SQL) - Wikipedia

en.wikipedia.org

Null (or NULL) is a special marker used in Structured Query Language to indicate that a data value does not exist in the database. Introduced by the creator of the relational database model, E. F. Codd...

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