Sql 使用另一个表中的列动态更新表

我有一个这样的顾客：

CREATE TABLE tbl_customer (
  id INTEGER,
  name VARCHAR(16),
  voucher VARCHAR(16)
);

CREATE TABLE tbl_voucher (
  id INTEGER,
  code VARCHAR(16)
);

UPDATE tbl_customer
SET voucher = (
    SELECT code
    FROM tbl_voucher
    WHERE code NOT IN (
        SELECT voucher
        FROM tbl_customer
        WHERE voucher IS NOT NULL
    )
    LIMIT 1
)
WHERE voucher IS NULL;

和这样的凭证表：

CREATE TABLE tbl_customer (
  id INTEGER,
  name VARCHAR(16),
  voucher VARCHAR(16)
);

CREATE TABLE tbl_voucher (
  id INTEGER,
  code VARCHAR(16)
);

UPDATE tbl_customer
SET voucher = (
    SELECT code
    FROM tbl_voucher
    WHERE code NOT IN (
        SELECT voucher
        FROM tbl_customer
        WHERE voucher IS NOT NULL
    )
    LIMIT 1
)
WHERE voucher IS NULL;

现在，假设customer表中始终有填充了id和名称的行，但是需要定期从

tbl\u凭证

表中插入凭证

重要提示：每张凭证只能分配给一个特定客户（即必须是唯一的）

我写了这样一个查询：

CREATE TABLE tbl_customer (
  id INTEGER,
  name VARCHAR(16),
  voucher VARCHAR(16)
);

CREATE TABLE tbl_voucher (
  id INTEGER,
  code VARCHAR(16)
);

UPDATE tbl_customer
SET voucher = (
    SELECT code
    FROM tbl_voucher
    WHERE code NOT IN (
        SELECT voucher
        FROM tbl_customer
        WHERE voucher IS NOT NULL
    )
    LIMIT 1
)
WHERE voucher IS NULL;

但是，这并不像预期的那样有效，因为查找未使用凭证的部分只执行一次，然后将所述凭证应用于每个客户

关于如何不用循环之类的编程结构来解决这个问题，有什么想法吗

还有一些示例数据，您可以想象我希望发生什么：

INSERT INTO tbl_customer VALUES (1, 'Sara', 'ABC');
INSERT INTO tbl_customer VALUES (1, 'Simon', 'DEF');
INSERT INTO tbl_customer VALUES (1, 'Andy', NULL);
INSERT INTO tbl_customer VALUES (1, 'Alice', NULL);

INSERT INTO tbl_voucher VALUES (1, 'ABC');
INSERT INTO tbl_voucher VALUES (2, 'LOL');
INSERT INTO tbl_voucher VALUES (3, 'ZZZ');
INSERT INTO tbl_voucher VALUES (4, 'BBB');
INSERT INTO tbl_voucher VALUES (5, 'CCC');

---

在执行了想要的查询之后，我希望Andy能得到凭证

LOL

，

Alice

应该得到

ZZZ

我猜这是MySQL。答案是这是一种痛苦。以下内容在

选择中指定值：

select c.*, v.voucher
from (select c.*, (@rnc := @rnc + 1) as rn
      from tbl_customer c cross join
           (select @rnc := 0) params
      where c.voucher is null
     ) c join
     (select v.*, (@rnv := @rnv + 1) as rn
      from tbl_vouchers v cross join
           (select @rnv := 0) params
      where not exists (select 1 from tbl_customers c where c.voucher = v.voucher)
     ) v
     on c.rn = v.rn;

您现在可以将其用于
更新
：

update tbl_customer c join 
       (select c.*, v.voucher
        from (select c.*, (@rnc := @rnc + 1) as rn
              from tbl_customer c cross join
                   (select @rnc := 0) params
              where c.voucher is null
             ) c join
             (select v.*, (@rnv := @rnv + 1) as rn
              from tbl_vouchers v cross join
                   (select @rnv := 0) params
              where not exists (select 1 from tbl_customers c where c.voucher = v.voucher)
             ) v
             on c.rn = v.rn
       ) cv
       on c.id = cv.id
    set c.voucher = cv.voucher;

请用您的RDBMSI标记。我实际上不确定正在使用什么RDBMS，这就是为什么我问您，如果不使用诸如循环之类的编程结构，是否可以做到这一点。我可以告诉你的是，查询将作为“营销云”Nice one中“数据扩展”的一部分运行，这确实适用于mysql！我会检查这是否也适用于Salesforce。