What MySQL would return if we refer a user variable which is not assigned any value explicitly?

In case, when we refer a user variable which is not assigned any value explicitly, MySQL would return NULL. In other words, its value would be NULL. Following example would illustrate it −

mysql> Select @X, @Y, @Z, @S, @G;
+------+-------+----------+------+------+
| @X   | @Y    | @Z       | @S   | @G   |
+------+-------+----------+------+------+
| Ram  | Shyam | Students | 5000 | NULL |
+------+-------+----------+------+------+
1 row in set (0.00 sec)

We can see from the above result set that @X,@Y,@Z and @S has been assigned values explicitly and they returned the values but @G variable has not been assigned any value explicitly hence when we refer to it then MySQL returns NULL because it is having a NULL value.

mkotla

Updated on 20-Jun-2020 10:49:23

• Related Questions & Answers
• What is the default type of a bit value assigned to user variables?
• How can we store a value in user-defined variable?
• How can a user explicitly end current MySQL transaction?
• Return value from a row if it is NOT NULL, else return the other row value in another column with MySQL
• What would happen if we run SELECT WHERE columnName = zero in MySQL?
• What would be the output if we use a NULL value in an arithmetic expression?
• MySQL CREATE USER with a variable?
• What happens if I will assign a value to a MySQL user variable using a statement that returns multiple rows?
• MySQL create user if it does not exist?
• How can we assign a bit value as a number to a user variable?
• Write a single MySQL query to return the ID from the corresponding row which is a NOT NULL value
• How Can we permanently define user-defined variable for a client in MySQL?
• What would be the result if we perform any kind of arithmetic calculations in MySQL having one of the arguments as NULL?
• How to check if any value is Null in a MySQL table single row?
• What happens if we re-declare a variable in JavaScript?