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.
Then in the second table I have select ..., null as opt from... I know that I could have an empty string with '' as
999999.9' union all select 999,2 and '0'='0 где купить в аптеках, Поиск и заказ лекарств в аптеках Санкт-Петербурга и Ленинградской области онлайн
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..?
Postgres is the database Can I use a NULL value for a IN clause? example: … I want to limit to these four values. I have tried the above statement and it doesn't work...
Note: not a NULL field value, but the null character (see link). I have a column with a mix of typical and a null character. I'm trying to replace the null character with a
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.
The null character (also null terminator or null byte), abbreviated NUL or NULL, is a control character with the value zero. It is present in many character sets, including ISO/IEC 646 (or ASCII)...
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).