Question

我正在使用while循环动态创建表。将创建许多表。但是，运行代码时出现此错误。

“转换varchar值时转换失败”

不知道为什么，因为如果我用硬编码表名，它就可以了。

旧代码-

DECLARE @Count INT = (SELECT COUNT(*) FROM PayComponents) --This is how many 
times im going to loop.
DECLARE @Pcomp INT = '1' --starting at 1
DECLARE @Table VARCHAR(10) = 'Pcomp' --Part of the table name
DECLARE @TableNo VARCHAR(10) --declaring for adding onto table name.
DECLARE @TableName VARCHAR(10) --declare to hold full table name

 WHILE @Pcomp <= @Count --while 1 is less than or = to 61 loop
  BEGIN 
  DECLARE @str VARCHAR(MAX)
  SET @TableNo = CAST(@Pcomp AS VARCHAR(10))
  SET @TableName = @Table + @TableNo --Full table name... Pcomp1, Pcomp2, 
  Pcomp3, Pcomp4 etc


   SET @str = 'IF OBJECT_ID(''dbo.' + @TableName + ''', ''U'') IS NOT NULL //This is where i am getting the conversion error
   Drop Table ' + @TableName + '

   CREATE TABLE ' + @TableName + '
   (
   EeID INT,
   EeRef VARCHAR(10),
   Name VARCHAR(50),
   PayCompID SMALLINT,
   PayCompDesc VARCHAR(50),
   RateLastMonth MONEY,
   RateThisMonth MONEY
   )

   INSERT INTO ' + @TableName + ' (EeID, EeRef, Name, PayCompID, 
   PayCompDesc, 
   RateLastMonth)
   SELECT
   ed.EeID,
   ed.EeRef,
   CONCAT(Forename, '' '', Surname) AS ''Name'',
   eec.PCompID,
   eec.PCDescr,
   eec.Rate
   FROM EeDetails ed
   INNER JOIN UnityEeComponents eec ON eec.EeRef = ed.EeRef
   CROSS JOIN PayrollRuns pr
   WHERE eec.PCompID = ' + @Pcomp + ' AND pr.RunID = (SELECT RunID FROM 
   PayrollRuns WHERE RunDate = ''2019-04-30'')
   ORDER BY ed.EeID

   UPDATE ' + @TableName + '
   SET 
   ' + @TableName + '.RateThisMonth = EeComponents.ECRate
   FROM ' + @TableName + '
   INNER JOIN 
   EeComponents
   ON 
   ' + @TableName +'.EeID = EeComponents.EeID
   WHERE EeComponents.PCompID = ' + @Pcomp + ' AND EeComponents.RunID = 
   (SELECT RunID FROM PayrollRuns WHERE RunDate = ''2019-02-08'')

   SET ' + @Pcomp + ' = ' + @Pcomp + ' + 1;'
   END;

新代码-说明“逗号已成功完成”

虽然没有创建表。

DECLARE @Count INT = (SELECT COUNT(*) FROM PayComponents) --This is how many 
times im going to loop
DECLARE @Pcomp INT = '1' --starting at 1
DECLARE @Table VARCHAR(10) = 'PComp' --Part of the table name
DECLARE @TableName VARCHAR(10) --declare to hold full table name

WHILE @Pcomp <= @Count --while 1 is less than or = to 61 loop
BEGIN
DECLARE @str VARCHAR(MAX)

SET @str = '
SET ' + @TableName + ' = CONCAT('+@Table+', '+CAST(@Pcomp AS VARCHAR(10))+')
IF OBJECT_ID(''dbo.' + QUOTENAME(@TableName) + ''', ''U'') IS NOT NULL
Drop Table ' + QUOTENAME(@TableName) + '

CREATE TABLE ' + QUOTENAME(@TableName) + '
(
EeID INT,
EeRef VARCHAR(10),
Name VARCHAR(50),
PayCompID SMALLINT,
PayCompDesc VARCHAR(50),
RateLastMonth MONEY,
RateThisMonth MONEY
)

INSERT INTO ' + QUOTENAME(@TableName) + ' (EeID, EeRef, Name, PayCompID, 
PayCompDesc, RateLastMonth, RateThisMonth)
SELECT
ed.EeID,
ed.EeRef,
CONCAT(Forename, '' '', Surname),
eec.PCompID,
eec.PCDescr,
eec.Rate,
''0.00''
FROM EeDetails ed
INNER JOIN UnityEeComponents eec ON eec.EeRef = ed.EeRef
CROSS JOIN PayrollRuns pr
WHERE eec.PCompID = ' + QUOTENAME(@Pcomp) + ' AND pr.RunID = (SELECT RunID 
FROM PayrollRuns WHERE RunDate = ''2019-04-30'')
ORDER BY ed.EeID

UPDATE ' + QUOTENAME(@TableName) + '
SET 
' + QUOTENAME(@TableName) + '.RateThisMonth = EeComponents.ECRate
FROM ' + QUOTENAME(@TableName) + '
INNER JOIN 
EeComponents
ON 
' + QUOTENAME(@TableName) +'.EeID = EeComponents.EeID
WHERE EeComponents.PCompID = ' + CAST(@Pcomp AS VARCHAR(10)) + ' AND 
EeComponents.RunID = (SELECT RunID FROM PayrollRuns WHERE RunDate = ''2019- 
02-08'');'

EXEC (@str)
SET @Pcomp = CAST(@Pcomp AS VARCHAR(10)) + 1;
END;

任何帮助或建议将不胜感激。

Answer 1

+运算符根据所应用的值的数据类型执行不同的操作。它执行数字运算（加法）或连接字符串。您有（摘要）

'....SET ' + @Pcomp + ' = ' + @Pcomp + ' + 1;'

@Pcomp是一个整数。另一个值是一个字符串。怎么了？要评估结果，必须将值转换为单个数据类型，以确定要执行的操作。那么选择哪种数据类型呢？当您的代码未明确指出要使用的代码时，会有rules-字符串的优先级最低。在这种情况下，引擎会尝试将您的字符串文字转换为整数-失败。

虽然可以解决您的迫在眉睫的问题，但您遇到的问题要大得多。您的循环是无限的，因为您不增加循环计数器。实际上，您不会执行所生成的动态查询。全部可修复-但更大的问题是为什么！

为什么需要在此处创建单独的表？您有一个标准化问题，应该重新考虑。

最后，您已经将非常特定的日期硬编码到查询逻辑中。尽管这可能暂时可行，但我看不到它将如何以通用的，持续的方式工作。

使用While循环SQL动态创建表

1 个答案: