What kind of Errors the SELECT statement can raise??

Question

In what cases? How to avoid them? How to handle them?

Evgeny.Br · Answer

Thanks very helpfull

ytram5 · Answer

Probably the most common mistake(at least for me) is to format an inline SQL statement incorrectly(don't leave a space when breaking to a new line for readability mostly). Another common mistake is to attempt to read a NULL value using a DataReader. To avoid this use the IsDbNull method of the Sql/OleDb DataReader class. Here's an example: SqlCommand cmd = new SqlCommand(); ... SqlDataReader sqr = cmd.ExecuteReader(); if(sqr.Read()) { if(sqr.IsDbNull(0)) { int a = sqr.GetInt(0); } } ... Yasser also had very good advice, always put the Connection close() call in the finally block of a try/catch. This will ensure that the database won't have unnecessary open connections.

yasser_8227 · Answer

Select statement can raise syntax error or null value error. One of the best way to avoid it is to test your query against the database in SQL Query Analyzer. This will show you guaranteed result what your query is returning before you use it in your programme. To catch exception thrown by database use try catch block: try { . . //database code . . }catch(SqlException or OleDbException) //use SqlException for SqlServer and for rest OleDbException . //catch any database exception here . } finally { //close your database connection here. So even if error is generated your database will not remain open } } Cheers, Yasser

What kind of Errors the SELECT statement can raise??

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