I have developed a query, and in the results for the first three columns I get NULL. How can I replace it with 0?
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.
In postgres, I'm getting an error when I try to union two tables where one table has a column (Amount) containing double precision data type...
Then in the second table I have select ..., null as opt from... I know that I could have an empty string with '' as
How can I run a MySQL query that selects everything that is not null? It would be something like … Do I just remove the all and go..?
What is the difference between … and … and why does the latter not work?
Note: A NULL value is different from a zero value or a field that contains spaces.
Предикат IS NULL позволяет проверить отсутствие (наличие) значения в полях таблицы. Использование в этих случаях обычных предикатов сравнения может привести к неверным результатам, так как сравнение со значением NULL дает результат UNKNOWN (неизвестно).
R language supports several null-able values and it is relatively important to understand how these
The IS NOT NULL condition is used in SQL to test for a non-NULL value. It returns TRUE if a non-NULL value is found, otherwise it returns FALSE. It can be used in a SELECT, INSERT, UPDATE, or DELETE statement.