MySQL-də || xüsusiyyəti

MySQL testi həll etməkdə köməklik göstərərdiz zəhmət olmasa 🙂

You work as database adminstrator for company inc.
You have written following statement:

SELECT ‘Student Name’||stud_name
FROM students
WHERE stud_id=50;

Which of the following will be treated as a number literal in the SELECT statement?

A.50
B.stud_id
C.||
D.Student Name

1. CREATE TABLE students (
stud_id INT(3) NOT NULL,
stud_name VARCHAR(25) NOT NULL,
stud_phone INT(11) NOT NULL,
stud_adress VARCHAR(50) NOT NULL
)

2. INSERT INTO students VALUES(50,’John’,11111111,’New York’);

3. mysql> SELECT ‘Student Name’||stud_name
-> FROM students
-> WHERE stud_id=50;
+—————————+
| ‘Student Name’||stud_name |
+—————————+
| 0 |
+—————————+
1 row in set, 2 warnings (0.00 sec)

4. Həm də niyə output=0 olur ki? 🙂