check if select statement returns null c#

Open(); // query to check whether value exists string sql . ExecuteNonQuery...

Open(); // query to check whether value exists string sql . ExecuteNonQuery returns the number of rows affected (if certain options are not.

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Read()) { // The command returns Row(s) } else { // No Row has been returne...

Read()) { // The command returns Row(s) } else { // No Row has been returned. } using (SqlCommand cmd = new SqlCommand(query, connection)) { using if it has data, the data will be in dwn.220.v.ua cmd = new MySqlCommand()) { MySqlDataReader rdr = null; string[] dados_bd = new string[2]; conn.

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dwn.220.v.ua() returns true if there are more rows to read. First time only...

dwn.220.v.ua() returns true if there are more rows to read. First time only if it is false that means reader has no data. if(!dwn.220.v.ua()) //Your.

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If the value in the database is null, the query returns dwn.220.v.ua Altern...

If the value in the database is null, the query returns dwn.220.v.ua Alternatively, you could use ExecuteReader, then check whether returned.

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There are at least two issues here. Firstly, you're calling BeginExecu...

There are at least two issues here. Firstly, you're calling BeginExecuteNonQuery - that doesn't return an integer, it returns an IAsyncResult.

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If its acceptable to return no results, check the value returned from Execu...

If its acceptable to return no results, check the value returned from ExecuteScalar() By definition, ExecuteScalar will return null if there are no results. SqlCommand sqlid = new SqlCommand("SELECT TOP 1 Proj_id FROM try { //Execute your SQL-statement here } catch(SqlException) { //If you want.

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string test = " select COUNT(*) from(select case when (SELECT count(*)...

string test = " select COUNT(*) from(select case when (SELECT count(*) then 1 else null end Num)x where Num is not null". which returns 2 if both the conditions are true, 1 if any one of them is true and 0 if both are false.

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It is the job of the C# Runtime Binder to decide on the actual data type Th...

It is the job of the C# Runtime Binder to decide on the actual data type The Query method does not return null if there are no matching rows.

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returned by the linq to sql query listed below as being null. . If FirstOrD...

returned by the linq to sql query listed below as being null. . If FirstOrDefault returns a value-type result, you need to check if there is a result.

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To create an SQL statement returning a single value using a TableAdapter If...

To create an SQL statement returning a single value using a TableAdapter If you already have a query on your TableAdapter that uses an SQL If you are not sure if your query requires parameters, or what parameters it requires, then check If the column allows null values, the return value is one of the nullable types.

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Executes the query, and returns the first column of the first row in the re...

Executes the query, and returns the first column of the first row in the result set row in the result set, or a null reference (Nothing in Visual Basic) if the result set A typical ExecuteScalar query can be formatted as in the following C# example.

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I don't know about C#, but in VB you can't test ExecuteScalar = n...

I don't know about C#, but in VB you can't test ExecuteScalar = null like that - you have HasRows to check if the query returns a result or not.

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Alternatively, if no such row exists, the SELECT statement returns a value ...

Alternatively, if no such row exists, the SELECT statement returns a value of NULL, By providing updates through a stored procedure, you can test to see if the.

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What if I called Select before the FirstOrDefault() to get the value of the...

What if I called Select before the FirstOrDefault() to get the value of the other than what I'm returning in the Select part of the statement.

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Close(); You can use the IsClosed property to check if the data reader is c...

Close(); You can use the IsClosed property to check if the data reader is closed, Checking for Null Values in Columns Null values can be a burden to deal with, dictates that a comparison made in a SELECT statement always returns false.

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