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.
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
What is the difference between … and … and why does the latter not work?
Hours 1 1 2 null null null. The result must be: 3. My query is: select count(distinct hour) from hours
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..?
Note: A NULL value is different from a zero value or a field that contains spaces.
Union select null, null, null, null, null, null, null from information_schema.tables. for a small database containing three tables. this instruction is used in sql injection I tried it and it worked but I didn't really know how it works can somebody help me...
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...
The IS NOT NULL condition is used in SQL to test for a non-NULL value.