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SQL using If Not Null on a Concatenation - Stack Overflow

stackoverflow.com

If I have the table … This will display Firstname-Middlename-Surname e.g. … The second one (Jane’s) displays correct, however since John doesn’t have a middlename, I want it to ignore the second dash.

sql - Counting null and non-null values in a single... - Stack Overflow

stackoverflow.com

SELECT COUNT(*), 'null_tally' AS narrative FROM us WHERE a IS NULL UNION SELECT COUNT(*), 'not_null_tally' AS narrative FROM

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.

oracle10g - Oracle: Concat with delimiter, but only if... - Stack Overflow

stackoverflow.com

I want to select a concatenation of a couple of fields, but with a separator between them. The separator should only be there if both operands are not null.

MySQL 8.0 Reference Manual :: B.6.4.3 Problems with NULL Values

dev.mysql.com

mysql> SELECT NULL, 1+NULL, CONCAT('Invisible',NULL); To search for column values that are NULL, you cannot use an expr = NULL test. The following statement returns no rows, because expr = NULL is never true for any expression: Press CTRL+C to copy. mysql> SELECT * FROM my_table...

SQL is null and = null - Stack Overflow

stackoverflow.com

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

MySQL CONCAT() Function

www.w3schools.com

SELECT CONCAT("SQL ", "Tutorial ", "is ", "fun!") AS ConcatenatedString; Try it Yourself ». Definition and Usage. The CONCAT() function adds two or more expressions together. Note: Also look at the CONCAT_WS() function. Syntax.

Confusing SQL error in SELECT NULL, *, NULL, NULL - Stack Overflow

stackoverflow.com

The Background I was trying to solve the fourth realistic mission in hackthissite.org, and couldn't figure out exactly what SQL I should inject into the URL to retrieve the list of emails.

Заметка про NULL / Хабр

habr.com

Существуют специальные операторы IS NULL и IS NOT NULL, которы�� позволяют производить сравнения с NULLами.

SQL NULL Values - IS NULL and IS NOT NULL

www.w3schools.com

The IS NULL operator is used to test for empty values (NULL values). The following SQL lists all customers with a NULL value in the "Address" field: Example. SELECT CustomerName, ContactName, Address FROM Customers WHERE Address IS NULL

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