Update data in Microsoft access database?

Question

1.00/5 (2 votes)

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I get this error:-System.Data.OleDb.OleDbException: 'Data type mismatch in criteria expression.'

What I have tried:

C#

private void UPDATE_Click(object sender, EventArgs e)
        { 
            con.Open();
            OleDbCommand cmd = con.CreateCommand();
            cmd.CommandType = CommandType.Text;
            cmd.CommandText = "update Test_1 set [IMAGE_PATH]= '" + t3.Text + "', [STON_ON] = '" + t4.Text + "', [TYPE] = '" + t5.Text + "', [VALUE] = '" + t6.Text + "' WHERE  [STON_ID] = '" + t2.Text + "'";
            cmd.ExecuteNonQuery();
            con.Close();
            MessageBox.Show("record update successfully...");
        }

Posted 19-Jan-23 18:34pm

Member 15746979

Updated 20-Jan-23 1:43am

PIEBALDconsult

v3

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Comments

Richard MacCutchan 20-Jan-23 8:17am

Chances are that the VALUE column is numeric, not text. See also OriginalGriff's comments in Solution 2. Also, do not post messages like "record update successfully...", when you have ignored the return value from your call to ExecuteNonQuery, so you have no idea whether it was successful or not.

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OriginalGriff · Answer 1 · 2023-01-19T19:47:00

Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.

When you concatenate strings, you cause problems because SQL receives commands like:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'

The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;--'

Which SQL sees as three separate commands:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';

A perfectly valid SELECT

SQL

DROP TABLE MyTable;

A perfectly valid "delete the table" command

SQL

--'

And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.

So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?

Sandeep Mewara · Answer 2 · 2023-01-19T19:18:00

Quote:
System.Data.OleDb.OleDbException: 'Syntax error in UPDATE statement.'

Pretty much clear on the reason of the error. Use IDE debugger and stop at the line post commandText to see what was formed there and you will be able to figure out the issue quickly. If there is anything specific with the values which is causing it.

Though to start with, believe it would be because you are using one of the columns which is a reserved word in SQL. Word is VALUE.
Refer: Reserved Keywords (Transact-SQL) - SQL Server | Microsoft Learn[^]

A quick solve would be to escape it using [].
Something line, ...[VALUE] = ...

BTW, would definitely not suggest above way to talk to database. It is open for SQL Injection and thus not a good practise. Use parameterized query.
Read about protecting from SQL Injection here: SQL Injection Mitigation: Using Parameterized Queries[^]

Following will help you learn about debugging:
Tutorial: Debug Visual Basic code - Visual Studio | Microsoft Docs[^]
First look at the debugger - Visual Studio | Microsoft Docs[^]

Update data in Microsoft access database?

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