I have this simple flow in Talend DI 6 (simplified for posting on SO):
The last step crashes with a NullPointerException, because missing XML attributes are returned as null.
Is there a way to get empty string values instead of nulls?
For now I'm using a tReplace step to remove nulls as a work-around, but it's tedious and adds to the cost of maintenance by creating one more place where the list of attributes needs to be maintained.
In Talend DI 5.6.2 it is possible to add default data values to the schema. The column in the schema is called "Default". If you expect strings, you can set an empty string, which is set if the column value is null:
Talend schema view with Default column
Works also for other data types. Talend DI 6 should still be able to do this, although the field might be renamed.
I store data in T-SQL server and use nchar fields to store string values.
The problem is that after selecting element from database I have very long string ended with spaces.
Can I set another field in database to avoid such situation, or have I do it in my ORM?
Rewrite the DB to store string values as nvarchar if it better represents your data.
If rewriting your DB is not possible or practical, then you have to trim the trailing spaces in your ORM.
Adding to the other answer. You can also deal with it in the select
RTRIM
A situation to use char or nchar is to prevent fragmentation.
If value starts null but you are going to later add a value then space is reserved.
I am facing this problem due to unknown reason and I have tried every forum and blog for solving this but could not get any satisfactory answer for this.
Let me describe the scenario.
I have a view in database which is consisting columns from two tables. None of the tables have any column with data type "int" hence the resultant view (let's name is "MyRecord") also does not have any column with "int" data types. All the columns in the view have varchar as datatype.
Now, in my .edmx I am adding this view and the model is created (with name "MyRecord") fine with all the properties are created fine with datatype "String". I am using Silverlight with RIA services, to after builing the application related proxies are also created fine without any confiction.
The problem starts when I try to query the "MyRecord" using my domain context, I am getting following error.
Load operation failed for query 'GetMyRecords'. The 'CenterCode' property on 'MyRecord' could not be set to a 'String' value. You must set this property to a non-null value of type 'Int32'.
As seen in the error, it is clearly forcing me to convert data type of "string" column "CenterCode" to the "Int32" which is totally useless and unnecessary for me. The "String" or "varchar" columns are there because they have some business importance and changing them to "Int32" or "int" might break the application in future. Its true that "CenterCode" column has numeric data only in it but there can be character data in future thats why it is created with 'varchar' datatype.
I can not change type of my data just because EF is not supporting.
I used sql server profiler, the query is being executed correct and I can run the same query in SSMS without any error. The error comes in the application only when EF is building objects from the data returned by the query.
I am failed to understand why Entity Framework is throwing this error, it is simply not converting "varchar" to "String" and unnecessarily bringing "Int32" in picture and making the life difficult. I am struggling with this issue since last 4 hours and tried every possible way to resolve it but everything is in vein.
Please provide some information or solution on this if anyone is having it.
EF team, you must have some answer to this question or work around for this problem.
I had the same problem with a double datatype.
Solution:
Change your view/procedure and cast the column like:cast(columnname as int32)
Not sure if you solved this problem or not, but I just ran into something like this while working on multiple result sets with EF. In my case, I had reader.NextResult() that was causing a problem for me because I hadn't read all the records from the previous result and I think EF was failing due to trying to map data from the second result set into the first object.
CAST(columnName as Type) solve my problem in stored procedure.
Somehow when doing an import of data into mysql using a multi-row insert with execute() function, there were many rows added with the string NULL for some columns.
How can I convert those NULL strings into MySQL NULL values so that I can check for empty values using is_null() in php when displaying data.
How can I avoid this problem? I was using the quote() function for each piece of data. Was that the problem using quote on empty fields? I was importing a csv file.
thank you
To insert an SQL NULL or any other expression, you can use a Zend_Db_Expr object. Even if you use quote(), ZF passes these objects through unquoted.
$null = new Zend_Db_Expr("NULL");
$table = new MyTable();
$table->insert(123, "abc", $null);
Note that because use of Zend_Db_Expr bypasses both quoting and parameterization, you're responsible for protecting against SQL injection.
This is tangential to your question, but consider LOAD DATA INFILE if you're bulk-loading a CSV file. It can be 20x faster than even using multi-row INSERT.
Null value means
No value
Inapplicable,unassigned, unknown, or unavailable
Which is true?
It's all about the context in which it's used. A null means there is no value but the reason for this will depend on the domain in which it is being used. In many cases the items you've listed are all valid uses of a null.
It can mean any of those things (and it is not always obvious which), which is one argument against using nulls at all.
See: http://en.wikipedia.org/wiki/Null_(SQL)#Controversy
From Wikipedia
Null is a special marker used in
Structured Query Language (SQL) to
indicate that a data value does not
exist in the database. Introduced by
the creator of the relational database
model, E. F. Codd, SQL Null serves to
fulfill the requirement that all true
relational database management systems
(RDBMS) support a representation of
"missing information and inapplicable
information". Codd also introduced the
use of the lowercase Greek omega (ω)
symbol to represent Null in database
theory. NULL is also an SQL reserved
keyword used to identify the Null
special marker.
Obviously you have the DB definition of what null means, however to an application it can mean anything. I once worked on a strange application (disclaimer- I didn't design it), that used null in a junction table to represent all of the options (allegedly it was designed this way to "save space"). This was a DB design for user and role management.
So null in this case meant the user was in all roles. That's one for daily WTF. :-)
Like many people I tend to avoid using nulls where realistically possible.
null indicates that a data value does not exist in the database, thus representing missing information.
Also allows for three-way truth value; true, false and unknown.
The only answer supported by SQL semantics is "unknown." If it meant "no value," then
'Hi there' = NULL
would return FALSE, but it returns NULL. This is because the NULL value in the expression means an unknown value, and the unknown value could very well be 'Hi there' as far as the system knows.
NULL is a representation that a field has not had a value set, or has been re-set to NULL.
It is not unknown or unavailable.
Note, that when looking for NULL values, do not use '=' in a where clause, use 'is', e.g.:
select * from User where username is NULL;
Not:
select * from User where username = NULL;
NULL, in the relational model, means Unknown. It's a mark that appears instead of a value wherever a value can appear in SQL.
Null means nothing, unknown and no value.
It does not mean unavailable or in applicable.
Null is a testable state of a column in a row, but it has no value itself.
By example:
An int can be only ...,0,1,2,3,... and also NULL.
An datetime can be only a valid date... and also NULL.
A bit can be only 0 or 1... and also NULL.
An varchar can be a string... and also NULL.
see the pattern?
You can make a column NOT NULL-able so that you can force a column to take a value.
The NULL SQL keyword is used to represent either a missing value or a value that is not applicable in a relational table
all :-)
if you want to add a semantic meaning to your field, add an ENUM
create TABLE myTable
(
myfield varchar(50)
myfieldType enum ('OK','NoValue','InApplicable','Unassigned','Unknown','Unavailable') NOT NULL
)