What is the difference between … and … and why does the latter not work?
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.
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..?
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...
I have developed a query, and in the results for the first three columns I get NULL. How can I replace it with 0?
Then in the second table I have select ..., null as opt from... I know that I could have an empty string with '' as
Note: A NULL value is different from a zero value or a field that contains spaces.
Специальное значение NULL означает отсутствие данных, констатацию того факта, что значение неизвестно. По умолчанию это значение могут принимать столбцы и переменные любых типов, если только на них не наложено ограничение NOT NULL.
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...
union all select null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null