¿Puedes unirte con valores NULL?

Can you join on NULL values?

Since it’s not possible to join on NULL values in SQL Server like you might expect, we need to be creative to achieve the results we want. One option is to make our AccountType column NOT NULL and set some other default value. In the above example we converted NULLs to the ` character.

Method 1. Use of ISNULL function – Here we just capturing the NULL value using ISNULL() function @ run-time and replacing it by -1, -1 is just and example, You can use any value you want. The value you select should not be present in the table you are joining.

The SQL LEFT JOIN returns all rows from the left table, even if there are no matches in the right table. This means that if the ON clause matches 0 (zero) records in the right table; the join will still return a row in the result, but with NULL in each column from the right table.

MySQL provides several useful functions that handle NULL effectively: IFNULL , COALESCE , and NULLIF . The IFNULL function accepts two parameters. The IFNULL function returns the first argument if it is not NULL , otherwise, it returns the second argument.

No, when you have NULL values in a column, these are never matched to other NULL values. If we inner joined these tables the same way, we would end up with the same result, because NULL values are not matched.

When using left join, right join, full (outer) join, it is possible to return NULL value, while (inner) join, cross join will not return NUll value.

Handling MySQL NULL Values

1. IS NULL − This operator returns true, if the column value is NULL.
2. IS NOT NULL − This operator returns true, if the column value is not NULL.
3. <=> − This operator compares values, which (unlike the = operator) is true even for two NULL values.

10 Tips to Handle Null Effectively

1. Don’t Overcomplicate Things.
2. Use Objects Methods as Stream Predicates.
3. Never Pass Null as an Argument.
4. Validate Public API Arguments.
5. Return Empty Collections Instead of Null.
6. Optional Ain’t for Fields.
7. Use Exceptions Over Nulls.
8. Test Your Code.