Question

我正在尝试调用过程内部的过程，但调用过程位于不同的数据库模式中，因此它是一个变量而不进行转换。

DECLARE client_database varchar(255);

SET client_database = get_database(_client_id); --this gets the schema the procedure is in

CALL client_database.client_procedure(); --then trying to call the procedure with the db schema variable however it's not translating

问题：为什么client_database没有翻译？

Answer 1

一种选择是使用13.5 Prepared SQL Statement Syntax：

mysql> DROP PROCEDURE IF EXISTS `client_procedure`;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> DROP PROCEDURE IF EXISTS  `server_procedure`;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> DROP DATABASE IF EXISTS `client_db`;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> DROP DATABASE IF EXISTS  `server_db`;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> CREATE DATABASE IF NOT EXISTS `client_db`;
Query OK, 1 row affected (0.00 sec)

mysql> CREATE DATABASE IF NOT EXISTS `server_db`;
Query OK, 1 row affected (0.00 sec)

mysql> DELIMITER //

mysql> CREATE PROCEDURE `client_db`.`client_procedure`()
    -> BEGIN
    ->   SELECT CONCAT('FROM `', DATABASE(), '`');
    -> END//
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE PROCEDURE `server_db`.`controller_procedure`()
    -> BEGIN
    ->   DECLARE `client_database` VARCHAR(64);
    -> 
    ->   -- This gets the schema the procedure is in
    ->   -- SET `client_database` := `get_database`(`client_id`);
    ->   SET `client_database` := 'client_db';
    -> 
    ->   SET @`call` := CONCAT('CALL `', `client_database`, '`.`client_procedure`');
    ->   PREPARE `stmt` FROM @`call`;
    ->   EXECUTE `stmt`;
    ->   DEALLOCATE PREPARE `stmt`;
    -> END//
Query OK, 0 rows affected (0.00 sec)

mysql> DELIMITER ;

mysql> CALL `server_db`.`controller_procedure`;
+-----------------------------------+
| CONCAT('FROM `', DATABASE(), '`') |
+-----------------------------------+
| FROM `client_db`                  |
+-----------------------------------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

请参阅db-fiddle。

从过程调用过程

1 个答案: