Question

我有一个varchar（5）字段。我需要在所有记录中找到第一个未使用的数字，以便它们以前导零开头。就像有一个00001和00003我想要查询返回00002.此外，许多记录包含字母，看起来像'G0542'。这些可以忽略不计。

我知道我很亲密。这似乎适用于SQL Server 2005，但不适用于2008或2012

create table b_addr ( inst_no varchar(5) Unique );
insert into b_addr (inst_no) values ('00001');
insert into b_addr (inst_no) values ('00002');
insert into b_addr (inst_no) values ('00004');
--this is the problem line 
insert into b_addr (inst_no) values ('A0045');

With usedNos as( 
select  CAST(b_addr.inst_no AS INT) as inst 
from b_addr 
where b_addr.inst_no LIKE '[0-9][0-9][0-9][0-9][0-9]') 
SELECT 
RIGHT('00000' + CONVERT(VARCHAR(5), COALESCE(min(inst)+1, 0)),5) AS next_inst_no 
from usedNos where not exists (select null from usedNos usn where usn.inst = usedNos.inst +1)

我如何构建它以便它也可以在sql server 2008+中使用？

Answer 1

以下是您的查询版本：

With usedNos as ( 
      select CAST(case when isnumeric(b_addr.inst_no) = 1
                       then b_addr.inst_no 
                  end AS INT) as inst 
      from b_addr 
     ) 
SELECT RIGHT('00000' + CONVERT(VARCHAR(5), COALESCE(min(inst)+1, 0)),5) AS next_inst_no 
from usedNos
where inst is not null and 
      not exists (select 1
                  from usedNos usn
                  where usn.inst = usedNos.inst +1
                 );

关键是在isnumeric()内使用case。这可以保证除非值看起来像数字，否则不会尝试cast()。如果它看起来不像数字，那么结果是NULL，它会在外部where子句中被过滤掉。

您的where条款：

      where b_addr.inst_no LIKE '[0-9][0-9][0-9][0-9][0-9]'

尝试做同样的事情。但是，SQL Server不保证在where之前处理select子句 - 这就是您收到意外错误的原因。

Answer 2

您可以检查您尝试投射的号码是否为实数：

而不是

CAST(b_addr.inst_no AS INT) as inst

执行类似

的操作

CAST(CASE WHEN ISNUMERIC(b_addr.inst_no) = 1 THEN b_addr.inst_no ELSE 0 END AS INT) as inst

这有点令人费解，但它确实有效。

演示：http://sqlfiddle.com/#!3/1aee5/6

Answer 3

create table b_addr ( inst_no varchar(5) Unique );
insert into b_addr (inst_no) values ('00001');
insert into b_addr (inst_no) values ('00002');
insert into b_addr (inst_no) values ('00004');
--this is the problem line 
insert into b_addr (inst_no) values ('A0045');

--Specify how many of the "next" unused numbers you want.
DECLARE @HowMany INT = 10

--Common Table Expression construct to generate sequential numbers.
;WITH 
  L0   AS(SELECT 1 AS c UNION ALL SELECT 1),
  L1   AS(SELECT 1 AS c FROM L0 AS A, L0 AS B),
  L2   AS(SELECT 1 AS c FROM L1 AS A, L1 AS B),
  L3   AS(SELECT 1 AS c FROM L2 AS A, L2 AS B),
  L4   AS(SELECT 1 AS c FROM L3 AS A, L3 AS B),
  L5   AS(SELECT 1 AS c FROM L4 AS A, L4 AS B),
  L6   AS(SELECT 1 AS c FROM L5 AS A, L5 AS B),
  SequentialNumbers AS(SELECT ROW_NUMBER() OVER(ORDER BY c) AS Num FROM L6)
SELECT TOP(@HowMany) RIGHT('00000' + CAST(sn.Num AS VARCHAR), 5) AS NextNumbers
FROM SequentialNumbers sn
WHERE sn.Num NOT IN ( 
    SELECT  CAST(b_addr.inst_no AS INT) AS inst 
    FROM b_addr 
    WHERE b_addr.inst_no LIKE '[0-9][0-9][0-9][0-9][0-9]'
)

Answer 4

这是另一个使用patindex而不是喜欢的人。

http://sqlfiddle.com/#!6/1aee5/12

With usedNos as( 
    select   b_addr.inst_no  as inst 
    from b_addr 
    where patindex('[0-9][0-9][0-9][0-9][0-9]',b_addr.inst_no) > 0
    ) 

SELECT 
RIGHT('00000' + COALESCE(cast((min(cast(inst as int)) + 1) as varchar), '00000'),5) AS next_inst_no 
from usedNos 
where not exists (select null from usedNos usn where  cast(usn.inst as int) = cast(usedNos.inst as int) + 1  )

--should return 00003, trying to find the first unused inst_no and padd it with zeros to make it 5 chars.

用零填充的varchar（5）字段中的第一个未使用的数字

4 个答案: