Question

我有一个mysql查询作为存储过程的一部分写入

-- {parameter}
SELECT id INTO emailId FROM email_list WHERE email = {email};

如果此查询返回空结果集，则emailId的值是多少？ undefined，null，0

我想检查emailId是否包含值并运行一系列插入。

我可以使用COUNT或IFNULL，但这意味着要声明另一个要检查的变量。如果可能，我想避免它。

*****************************编辑***************** ***********

DELIMITER $$
CREATE DEFINER=`root`@`localhost` PROCEDURE `addCustomer`(
    IN email1 VARCHAR(60),
    IN status1 VARCHAR(15),
    IN bill_pin_id SMALLINT UNSIGNED,
    IN bill_addr VARCHAR(175),
    IN bill_name VARCHAR(70),
    IN tel VARCHAR(15)
)
BEGIN
DECLARE emailId INT UNSIGNED DEFAULT 0;
DECLARE billAddrId INT UNSIGNED DEFAULT 0;
DECLARE custId INT UNSIGNED DEFAULT 0;
DECLARE orderId INT UNSIGNED DEFAULT 0;

DECLARE sqlError TINYINT DEFAULT FALSE;

DECLARE CONTINUE HANDLER FOR SQLEXCEPTION SET sqlError = true;


-- get id of email if it exists
SELECT id INTO emailId FROM email_list WHERE email = email1;

-- if email exists, check if a customer is listed

IF (emailId > 0) THEN

   SELECT id INTO custId FROM customer WHERE email_list_id = emailId;
   IF (custId > 0) THEN

      -- check for duplicate address in the address table

      SELECT address_id INTO billAddrId FROM customer_addr
          INNER JOIN address ON address_id = address.id
          WHERE customer_id = custId AND address = bill_addr;

   END IF;
END IF;

START TRANSACTION;

-- if emails isnt listed - no customer or address should exist
IF (emailId = 0) THEN
    INSERT INTO email_list (email, status) VALUES (email1, status1);
    SELECT LAST_INSERT_ID() INTO emailId;
    SELECT emailId;

    INSERT INTO customer (email_list_id, full_name, phone) VALUE (emailId, bill_name, tel);
    SELECT LAST_INSERT_ID() INTO custId;
    SELECT custId;

    INSERT INTO address (pincode_id, address) VALUES (bill_pin_id, bill_addr);
    SELECT LAST_INSERT_ID() INTO billAddrId;
    SELECT billAddrId;

    INSERT INTO customer_addr (address_id, customer_id) VALUES (billAddrId, custId);
    SELECT LAST_INSERT_ID();

    INSERT INTO orders (customer_id, order_status) VALUES (custId, 'pending');
    SELECT LAST_INSERT_ID() INTO orderId;

END IF;

IF sql_error = FALSE THEN
    COMMIT;
    SELECT 'SUCCESS';
ELSE
    ROLLBACK;
    SELECT 'FAILED';
END IF;

END$$
DELIMITER ;

我删除了代码中不必要的行以保持简短。

以下是select语句返回的值。所有表都是空的。但是以下值表示已插入行。但它仍然是空的。电子邮件ID 43

CUSTID 12

billAddrId 13

CustomerAddr 13

的orderId 8

Answer 1

您可以通过选择值来测试它：

for (int i = 2 ; i < 27 ; i++) {
    if (27 % i == 0) {
        System.out.println("Found the two numbers: " + i + " and " + 27 / i);
        break;
    }
}

这将返回drop procedure if exists test_proc; create procedure test_proc() begin DECLARE emailId INT UNSIGNED; SET emailId = 0; SELECT 123 INTO emailId FROM dual WHERE 1 = 2; SELECT emailId; end; call test_proc();，这意味着 - 如果没有找到行，则不会更改该值。

演示：http://rextester.com/MHRTL99697

Answer 2

为我工作

MariaDB [sandbox]> drop procedure  if exists p;
Query OK, 0 rows affected (0.06 sec)

MariaDB [sandbox]> delimiter $$
MariaDB [sandbox]> create procedure p(inid int)
    -> begin
    -> declare vid int;
    -> set vid = 0;
    -> select id into vid  from users  where id = inid;
    -> if vid = 1 then
    -> select 'found';
    -> else
    -> select 'notfound';
    -> end if;
    -> end $$
Query OK, 0 rows affected (0.05 sec)

MariaDB [sandbox]> delimiter ;
MariaDB [sandbox]>
MariaDB [sandbox]> call p(1);
+-------+
| found |
+-------+
| found |
+-------+
1 row in set (0.02 sec)

Query OK, 0 rows affected (0.02 sec)

MariaDB [sandbox]>
MariaDB [sandbox]> call p(1000);
+----------+
| notfound |
+----------+
| notfound |
+----------+
1 row in set (0.00 sec)

Query OK, 0 rows affected, 1 warning (0.01 sec)

MariaDB [sandbox]> show warnings;
+---------+------+-----------------------------------------------------+
| Level   | Code | Message                                             |
+---------+------+-----------------------------------------------------+
| Warning | 1329 | No data - zero rows fetched, selected, or processed |
+---------+------+-----------------------------------------------------+
1 row in set (0.00 sec)

查询返回的变量值（结果集为空）？

2 个答案: