What do MySQL user variables mean? How do we assign values ​​to them?

MySQL user variables are written as @variable, which can be set to an integer, real number, string, or NULL value. With the help of SET statement, we can assign values ​​to user variables. While assigning a value to a user variable, we can use = or := as assignment operator.

Example

mysql> SET @A = 100;
Query OK, 0 rows affected (0.00 sec)

mysql> Set @B = 'MySQL';
Query OK, 0 rows affected (0.00 sec)

The above query assigns the value 100 to user variable A and "MySQL" to user variable B respectively.

We can check their values ​​with the help of SELECT statement as shown below-

mysql> Select @A, @B;
+------+-------+
| @A   | @B    |
+------+-------+
| 100  | MySQL |
+------+-------+
1 row in set (0.05 sec)

We can also perform multiple variable assignments separated by commas. The following example illustrates this -

mysql> SET @X = 'Ram',@Y = 'Shyam',@Z = 'Students', @S = 5000;
Query OK, 0 rows affected (0.00 sec)

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

We can also assign values ​​to them using SELECT statement, but for this we have to use only := assignment operator instead of =. As shown in the following example -

mysql> SELECT @C := 'Tutorialspoint';
+------------------------+
| @C := 'Tutorialspoint' |
+------------------------+
| Tutorialspoint         |
+------------------------+
1 row in set (0.00 sec)

mysql> SELECT @C;
+----------------+
| @C             |
+----------------+
| Tutorialspoint |
+----------------+
1 row in set (0.00 sec)

The above is the detailed content of What do MySQL user variables mean? How do we assign values ​​to them?. For more information, please follow other related articles on the PHP Chinese website!