Variable Assignment : Variable « Select Clause « SQL / MySQL

1. SQL / MySQL
2. Select Clause
3. Variable

Variable Assignment

       
mysql>
mysql> CREATE TABLE mytable (
    ->     id INT AUTO_INCREMENT,
    ->     begintime DATETIME,
    ->     endtime DATETIME,
    ->     PRIMARY KEY (id)
    -> );
Query OK, 0 rows affected (0.01 sec)

mysql>
mysql> INSERT INTO mytable (begintime, endtime) VALUES
    ->         ('2005-03-27 7:15', '2005-03-27 18:00'),
    ->         ('2005-03-28 8:00', '2005-03-28 18:00'),
    ->         ('2005-03-29 7:30', '2005-03-29 16:50'),
    ->         ('2005-03-30 7:00', '2005-03-30 17:15');
Query OK, 4 rows affected (0.00 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql>
mysql>
mysql> SET @varname = 3;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT @varname := 3;
+---------------+
| @varname := 3 |
+---------------+
|             3 |
+---------------+
1 row in set (0.00 sec)

mysql> SELECT @varname := COUNT(*) FROM mytable;
+----------------------+
| @varname := COUNT(*) |
+----------------------+
|                    4 |
+----------------------+
1 row in set (0.00 sec)

mysql> SELECT COUNT(*) FROM mytable INTO @varname;
Query OK, 1 row affected (0.00 sec)

mysql> SELECT id, begintime FROM mytable WHERE id=1 INTO @t, @st;
Query OK, 1 row affected (0.00 sec)

mysql>
mysql>
mysql> drop table mytable;
Query OK, 0 rows affected (0.00 sec)

   
    
    
    
    
    
    
  

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