SQL Server query with null value

Question

In my C# code, I have to do an SQL Query like this :

context.ExecuteStoreQuery("SELECT * FROM MyTable WHERE Field0 = {0} AND 
    Field1 = {1}", field0, field1)

When field1 = null in c# and NULL in database this query doesn't work. (I have to use a different syntax with IS NULL)

How can I correct this without make an if (in reality, I have 10 fields...) ?

Answer 1

you can use the short variant of the if statement. I don't think you can handle your problem without an if statement. Example:

String.Format("SELECT * FROM MyTable WHERE Field0 {0} ", value==null ? "IS NULL" : String.Format("= {0}", value))

It is also possible to parameterize the query by using "@ParameterName"

context.ExecuteStoreQuery<ProductionUnit>(
  String.Format("SELECT * FROM MyTable WHERE Field0 {0} @Parameter1",
  value==null ? "IS", "="), new SqlParameter("@Parameter1", value));

Regards

Answer 2

public string appendCondition(String sqlQuery, String field, Object value)
{ 
 string resultQuery = sqlQuery + " " + value == null ? " IS NULL " : "=" + value.ToString();
 return resultQuery;
}

Hope you can add simple logic to add "WHERE" or "AND" by yourself.

Answer 3

By default, SQL server does not allow you to compare a value to null. All comparisons resolve to false, even those that are logically opposite. In other words, you can do:

where field = 1 and where field <> 1. If field is null, both logically resolve to false.

In any case, you need an explicit check for null in your query:

context.ExecuteStoreQuery(@"SELECT * FROM MyTable WHERE 
    (Field0 = {0} or (Field0 is null and {0} is null))  AND 
    (Field1 = {1} or (Field1 is null and {0} is null))", field0, field1)

Answer 4

well, the first thing i would do is remove the select *. BAD!

the second thing i would do is make this a stored procedure.

    create procedure dbo.MyTableSelect
    @field0 int,
    @field1 int=null
as
begin

    select
        *
    from MyTable
    where Field0=@field0
        and (@field1 is null or Field1=@field1)



end

you then can change your code to this

context.ExecuteStoreQuery("exec dbo.MyTableSelect @field0={0}, @field1 = {1}", field0, field1)