MySQL中预处理语句prepare、execute与deallocate的使用教

PREPARE stmt_name FROM preparable_stmt

EXECUTE stmt_name
 [USING @var_name [, @var_name] ...] -

{DEALLOCATE | DROP} PREPARE stmt_name

mysql> PREPARE pr1 FROM 'SELECT ?+?';
Query OK, 0 rows affected (0.01 sec)
Statement prepared

mysql> SET @a=1, @b=10 ;
Query OK, 0 rows affected (0.00 sec)

mysql> EXECUTE pr1 USING @a, @b;
+------+
| ?+? |
+------+
| 11 |
+------+
1 row in set (0.00 sec)

mysql> EXECUTE pr1 USING 1, 2; -- 只能使用用户变量传递。
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the 
right syntax to use near '1, 2' at line 1

mysql> DEALLOCATE PREPARE pr1;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE a (a int);
Query OK, 0 rows affected (0.26 sec)

mysql> INSERT INTO a SELECT 1;
Query OK, 1 row affected (0.04 sec)
Records: 1 Duplicates: 0 Warnings: 0

mysql> INSERT INTO a SELECT 2;
Query OK, 1 row affected (0.04 sec)
Records: 1 Duplicates: 0 Warnings: 0

mysql> INSERT INTO a SELECT 3;
Query OK, 1 row affected (0.04 sec)
Records: 1 Duplicates: 0 Warnings: 0

mysql> SET @select_test = CONCAT('SELECT  FROM ', @table_name);
Query OK, 0 rows affected (0.00 sec)

mysql> SET @table_name = 'a';
Query OK, 0 rows affected (0.00 sec)

mysql> PREPARE pr2 FROM @select_test;
Query OK, 0 rows affected (0.00 sec)
Statement prepared

mysql> EXECUTE pr2 ;
+------+
| a |
+------+
| 1 |
| 2 |
| 3 |
+------+
3 rows in set (0.00 sec)

mysql> DROP PREPARE pr2; -- 此处DROP可以替代DEALLOCATE
Query OK, 0 rows affected (0.00 sec)