Ошибка при преобразовании типа данных varchar к int

Microsoft SQL Server 2008 (SP1), getting an unexpected ‘Conversion failed’ error.

Not quite sure how to describe this problem, so below is a simple example. The CTE extracts the numeric portion of certain IDs using a search condition to ensure a numeric portion actually exists. The CTE is then used to find the lowest unused sequence number (kind of):

CREATE TABLE IDs (ID CHAR(3) NOT NULL UNIQUE);

INSERT INTO IDs (ID) VALUES ('A01'), ('A02'), ('A04'), ('ERR');

WITH ValidIDs (ID, seq)
AS 
(
 SELECT ID, CAST(RIGHT(ID, 2) AS INTEGER)
   FROM IDs 
  WHERE ID LIKE 'A[0-9][0-9]'
)
SELECT MIN(V1.seq) + 1 AS next_seq
  FROM ValidIDs AS V1
 WHERE NOT EXISTS (
                   SELECT * 
                     FROM ValidIDs AS V2
                    WHERE V2.seq = V1.seq + 1
                  );

The error is, ‘Conversion failed when converting the varchar value ‘RR’ to data type int.’

I can’t understand why the value ID = 'ERR' should be being considered for conversion because the predicate ID LIKE 'A[0-9][0-9]' should have removed the invalid row from the resultset.

When the base table is substituted with an equivalent CTE the problem goes away i.e.

WITH IDs (ID)
AS
(
 SELECT 'A01'
 UNION ALL 
 SELECT 'A02'
 UNION ALL 
 SELECT 'A04'
 UNION ALL 
 SELECT 'ERR' 
),
ValidIDs (ID, seq)
AS 
(
 SELECT ID, CAST(RIGHT(ID, 2) AS INTEGER)
   FROM IDs 
  WHERE ID LIKE 'A[0-9][0-9]'
)
SELECT MIN(V1.seq) + 1 AS next_seq
  FROM ValidIDs AS V1
 WHERE NOT EXISTS (
                   SELECT * 
                     FROM ValidIDs AS V2
                    WHERE V2.seq = V1.seq + 1
                  );

Why would a base table cause this error? Is this a known issue?

UPDATE @sgmoore: no, doing the filtering in one CTE and the casting in another CTE still results in the same error e.g.

WITH FilteredIDs (ID)
AS 
(
 SELECT ID
   FROM IDs 
  WHERE ID LIKE 'A[0-9][0-9]'

), 
ValidIDs (ID, seq)
AS 
(
 SELECT ID, CAST(RIGHT(ID, 2) AS INTEGER)
   FROM FilteredIDs 
)
SELECT MIN(V1.seq) + 1 AS next_seq
  FROM ValidIDs AS V1
 WHERE NOT EXISTS (
                   SELECT * 
                     FROM ValidIDs AS V2
                    WHERE V2.seq = V1.seq + 1
                  );

Microsoft SQL Server 2008 (SP1), getting an unexpected ‘Conversion failed’ error.

Not quite sure how to describe this problem, so below is a simple example. The CTE extracts the numeric portion of certain IDs using a search condition to ensure a numeric portion actually exists. The CTE is then used to find the lowest unused sequence number (kind of):

CREATE TABLE IDs (ID CHAR(3) NOT NULL UNIQUE);

INSERT INTO IDs (ID) VALUES ('A01'), ('A02'), ('A04'), ('ERR');

WITH ValidIDs (ID, seq)
AS 
(
 SELECT ID, CAST(RIGHT(ID, 2) AS INTEGER)
   FROM IDs 
  WHERE ID LIKE 'A[0-9][0-9]'
)
SELECT MIN(V1.seq) + 1 AS next_seq
  FROM ValidIDs AS V1
 WHERE NOT EXISTS (
                   SELECT * 
                     FROM ValidIDs AS V2
                    WHERE V2.seq = V1.seq + 1
                  );

The error is, ‘Conversion failed when converting the varchar value ‘RR’ to data type int.’

I can’t understand why the value ID = 'ERR' should be being considered for conversion because the predicate ID LIKE 'A[0-9][0-9]' should have removed the invalid row from the resultset.

When the base table is substituted with an equivalent CTE the problem goes away i.e.

WITH IDs (ID)
AS
(
 SELECT 'A01'
 UNION ALL 
 SELECT 'A02'
 UNION ALL 
 SELECT 'A04'
 UNION ALL 
 SELECT 'ERR' 
),
ValidIDs (ID, seq)
AS 
(
 SELECT ID, CAST(RIGHT(ID, 2) AS INTEGER)
   FROM IDs 
  WHERE ID LIKE 'A[0-9][0-9]'
)
SELECT MIN(V1.seq) + 1 AS next_seq
  FROM ValidIDs AS V1
 WHERE NOT EXISTS (
                   SELECT * 
                     FROM ValidIDs AS V2
                    WHERE V2.seq = V1.seq + 1
                  );

Why would a base table cause this error? Is this a known issue?

UPDATE @sgmoore: no, doing the filtering in one CTE and the casting in another CTE still results in the same error e.g.

WITH FilteredIDs (ID)
AS 
(
 SELECT ID
   FROM IDs 
  WHERE ID LIKE 'A[0-9][0-9]'

), 
ValidIDs (ID, seq)
AS 
(
 SELECT ID, CAST(RIGHT(ID, 2) AS INTEGER)
   FROM FilteredIDs 
)
SELECT MIN(V1.seq) + 1 AS next_seq
  FROM ValidIDs AS V1
 WHERE NOT EXISTS (
                   SELECT * 
                     FROM ValidIDs AS V2
                    WHERE V2.seq = V1.seq + 1
                  );

Есть 3 таблицы:

Покупатели — customer(id,name,city,phone,rating)
поставщики — supplier(id,name,city,phone)
договор — contract(id,cust_id,sup_id,date,sum)

Пытаюсь сделать приложение для работы с БД. На одной из форм для таблицы contract использую компонент DBLookupcomboboxEh. В нем появляется список покупателей, выбираю одну из фамилий, а в бд нужно занести его id. Аналогично с поставщиками. Проблема состоит в том, что при добавление новой записи(заключении нового договора) появляется такая ошибка: Ошибка при преобразовании типа данных varchar к int. Как я понимаю в DBLookupcomboboxEh отображается фамилия (тип nvarchar), а id (int). Подскажите пожалуйста как исправить эту ошибку.

Параметры DBLookupcomboboxEh вроде настроены правильно:

Для покупателей:
DataField-cust_id
DataSource-DataModule2.ContractDataSource
KeyField-id
ListField-name
ListSource-DataModule2.CustomerDataSource

C поставщиками аналогично.

Код (для добавления записи):

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procedure TForm5.btn1Click(Sender: TObject);
var cust_id, sup_id, date, sum: string;
 
begin
   cust_id:=QuotedStr(unit5.form5.dblkpcmbxhcust_id.text);
   sup_id:=QuotedStr(unit5.form5.dblkpcmbxhsup_id.text);
   dbdth2.Text:= DateToStr(dtp1.Date);
   date:=QuotedStr(unit5.form5.dbdth2.text);
   sum:=QuotedStr(unit5.form5.dbdth1.text);
 
   with Unit2.DataModule2.qry  do
   begin
     Close;
     SQL.Clear;
     SQL.Add('exec add_contract' +cust_id+','+sup_id+','+date+','+sum);
     Execsql;
     Unit2.DataModule2.ContractQuery.Active:=False;
     Unit2.DataModule2.ContractQuery.Active:=true;
   end;
end;

As per your table structure, there are 3 fields that are of numeric datatype. These are — contactno, pf_acc_no and basic_sal

And the values for these fileds are txtcont.Text, txtqibacc.Text and txtnetsalary.Text respectively, And your are also putting ' around them, that is why they are being treated as varchar filed.

While constructing the sql statement, you should pass the values for these fields as numeric, which is to say without ' marks. So just remove ' before and after these fields and your query should work fine.

SqlCommand cmd = new SqlCommand("INSERT INTO Employee(
     empcode,firstname,lastname,gender,address,contactno,bloodgroup,
    dateofbirth, country,qid,passportno,passportexpiredate,designation,
    doj,doexpid,pf_acc_no, agreementstartdate,agreementenddate,
    department,basic_sal,remarks,empimage) 
    VALUES('" + txtempcode.Text + "','" + txtfrstname.Text + "', 
    '" + txtlstname.Text + "','" + combogender.Text + "','" +
    txtaddr.Text + "'," + txtcont.Text + ",'" + txtblodgrp.Text + "', '" + 
    dob.Value.ToString("yyyy/MM/dd") + "' ,'" + txtcountry.Text + "','" + tqid.Text + "','" + 
    txtpassportno.Text + "', '" + passexpdate.Value.ToString("yyyy/MM/dd") + "' ,'" + 
    combodesig.Text + "', '" + doj.Value.ToString("yyyy/MM/dd") + "', '" + doexpqid.Value.ToString("yyyy/MM/dd") + "', " + 
    txtqibacc.Text + ", '" + agreestartdate.Value.ToString("yyyy/MM/dd") + "','" + agreeenddate.Value.ToString("yyyy/MM/dd") + "' ,'" + combobranch.Text + "'," + txtnetsalary.Text + ",'" + txtremark.Text + "',@empimage) ", cn);

In case you need to pass null to these numeric fields, use DBNull.Value as shown here —
Assign Null value to the Integer Column in the DataTable

Constructing queries like these are prone to SqlInjection, suggest to use parameterized queries instead.

While developing data processes in SQL Server, under certain circumstances, you might get the error message: error converting varchar to numeric. This error is similar with the conversion error you might get when you are trying to convert a varchar to float, etc.

Read on to find out the reason for getting this error message and how you can easily resolve it within just a minute.

The Numeric Data Type in SQL Server

Prior to discuss how you can reproduce and resolve the issue, it is important that you first understand the numeric data type in SQL Server. As described in the relevant MS Docs article, the numeric data type has fixed precision and scale, and it has equivalent functionality with the decimal data type.

Arguments

The numeric data type takes two arguments, that is precision and scale. The syntax is numeric(precision, scale).

Precision defines the maximum number of decimal digits (in both sides of the number) and its value range is between 1 and 38.

Scale, defines the number of decimal digit that will be stored to the right of the decimal point. Its value can range between 1 and the value specified for precision.

Here’s an example of a numeric data type value in SQL Server:

DECLARE @numValue NUMERIC(10,2);
SET @numValue=123456.7890

SELECT @numValue as NumValue;
GO

The number returned by the above T-SQL query is: 123456.7890

In the above example I specified as precision 10 and as scale 2.

So, even though I specified 123456.7890 as the numeric value, it was indirectly converted to a numeric(10,2) value and that’s why it returned the value 123456.79

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Reproducing the Conversion Error

Great. Now, let’s reproduce the conversion error by trying to convert a “problematic” varchar value to numeric.

You can find this example below:

DECLARE @valueToConvert VARCHAR(50);
SET @valueToConvert='1123,456.7890';

SELECT CAST(@valueToConvert AS NUMERIC(10,2)) as ConvertedNumber;
GO

When you execute the above T-SQL code, you will get the below exact error message:

Msg 8114, Level 16, State 5, Line 4
Error converting data type varchar to numeric.

How to Resolve the Conversion Error

As you might have observed in the above example, the @valueToConvert variable, besides the dot (.), it also contains a comma (,).

Therefore, at the time of its conversion to the numeric data type, the comma is considered an illegal character for the destination data type (numeric) and that’s why you get the error message.

In order to resolve the conversion error, you just need to remove the comma (,) from the varchar value that you want to convert to numeric.

Note: At this point, you also need to make sure that the varchar value to be converted, is the actual number you wish to convert to the numeric data type. Also, you need to make sure that you only use the decimal symbol, in this case the dot (.), and not any digit grouping symbols, etc.

So, if we remove the comma from the above example, we can see that the conversion is successful.

DECLARE @valueToConvert VARCHAR(50);
SET @valueToConvert='1123456.7890';

SELECT CAST(@valueToConvert AS NUMERIC(10,2)) as ConvertedNumber;
GO

Output:

In general, when converting varchar values to numbers (i.e. decimal, numeric, etc.), you need to be careful in order for your varchar value, not contain any digit grouping symbols (i.e. a comma) or any other characters that do not have a meaning as a number.

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How to resolve the error: Error converting varchar to numeric in SQL Server

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