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.
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...
If I have this - tadd is the Address table: … Is there a way to exclude the apt_number if it doesn't exist? I was thinking of: … But it will return only those rows with apt_number...
A field with a NULL value is a field with no value. If a field in a table is optional, it is possible to insert a new record or update a record without adding a value to this
Retrieve data from another database: 1 UNION ALL SELECT NULL,concat(0x28,column1,0x3a
Mapping to and from null. Null Propagates Through Expressions. Null in Aggregate Functions
First, it’s important to know what a NULL is in SQL. A NULL in SQL simply means no value exists for the field.
Чем опасен NULL? Сравнение NULL с любым другим значением, даже с родственным (в
In one of my MySQL queries, it can happen from time to time that in the results there is the one or the other NULL value, because the corresponding cell has not yet been added to the database. To nevertheless be able to process the values in my PHP script, I would like to make MySQL return the...
mysql> SELECT NULL, 1+NULL, CONCAT('Invisible',NULL); To search for column values that are NULL, you cannot use an expr = NULL test. The following statement returns no rows, because expr = NULL is never true for any expression: Press CTRL+C to copy. mysql> SELECT * FROM my_table...