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c# - Failed to enable constraints when filling datatable [duplicate]

I make an outer join and executed successfully in the informix database but I get the following exception in my code:
DataTable dt = TeachingLoadDAL.GetCoursesWithEvalState(i, bat);
Failed to enable constraints. One or more rows contain values
violating non-null, unique, or foreign-key constraints.
I know the problem, but I don't know how to fix it.
The second table I make the outer join on contains a composite primary key which are null in the previous outer join query.
EDIT:
SELECT UNIQUE a.crs_e, a.crs_e || '/ ' || a.crst crs_name, b.period,
b.crscls, c.crsday, c.from_lect, c.to_lect,
c.to_lect - c.from_lect + 1 Subtraction, c.lect_kind, e.eval, e.batch_no,
e.crsnum, e.lect_code, e.prof_course
FROM rlm1course a, rfc14crsgrp b, ckj1table c, mnltablelectev d,
OUTER(cc1assiscrseval e)
WHERE a.crsnum = b.crsnum
AND b.crsnum = c.crsnum
AND b.crscls = c.crscls
AND b.batch_no = c.batch_no
AND c.serial_key = d.serial_key
AND c.crsnum = e.crsnum
AND c.batch_no = e.batch_no
AND d.lect_code= e.lect_code
AND d.lect_code = ....
AND b.batch_no = ....
The problem happens with the table cc1assiscrseval. The primary key is (batch_no, crsnum, lect_code).
How to fix this problem?
EDIT:
According to #PaulStock advice:
I do what he said, and i get:
? dt.GetErrors()[0] {System.Data.DataRow} HasErrors: true ItemArray:
{object[10]} RowError: "Column 'eval' does not allow DBNull.Value."
So I solve my problem by replacing e.eval to ,NVL (e.eval,'') eval.and this solves my problem.
Thanks a lot.

This problem is usually caused by one of the following
null values being returned for columns not set to AllowDBNull
duplicate rows being returned with the same primary key.
a mismatch in column definition (e.g. size of char fields) between the database and the dataset
Try running your query natively and look at the results, if the resultset is not too large. If you've eliminated null values, then my guess is that the primary key columns is being duplicated.
Or, to see the exact error, you can manually add a Try/Catch block to the generated code like so and then breaking when the exception is raised:
Then within the command window, call GetErrors method on the table getting the error.
For C#, the command would be ? dataTable.GetErrors()
For VB, the command is ? dataTable.GetErrors
This will show you all datarows which have an error. You can get then look at the RowError for each of these, which should tell you the column that's invalid along with the problem. So, to see the error of the first datarow in error the command is:
? dataTable.GetErrors(0).RowError
or in C# it would be ? dataTable.GetErrors()[0].RowError

You can disable the constraints on the dataset. It will allow you to identify bad data and help resolve the issue.
e.g.
dataset.TableA.Clear();
dataset.EnforceConstraints = false;
dataAdapter1.daTableA.Fill(dataset, TableA");
The fill method might be slightly different for you.

This will find all rows in the table that have errors, print out the row's primary key and the error that occurred on that row...
This is in C#, but converting it to VB should not be hard.
foreach (DataRow dr in dataTable)
{
if (dr.HasErrors)
{
Debug.Write("Row ");
foreach (DataColumn dc in dataTable.PKColumns)
Debug.Write(dc.ColumnName + ": '" + dr.ItemArray[dc.Ordinal] + "', ");
Debug.WriteLine(" has error: " + dr.RowError);
}
}
Oops - sorry PKColumns is something I added when I extended DataTable that tells me all the columns that make up the primary key of the DataTable. If you know the Primary Key columns in your datatable you can loop through them here. In my case, since all my datatables know their PK cols I can write debug for these errors automatically for all tables.
The output looks like this:
Row FIRST_NAME: 'HOMER', LAST_NAME: 'SIMPSON', MIDDLE_NAME: 'J', has error: Column 'HAIR_COLOR' does not allow DBNull.Value.
If you're confused about the PKColumns section above - this prints out column names and values, and is not necessary, but adds helpful troubleshooting info for identifying which column values may be causing the issue. Removing this section and keeping the rest will still print the SQLite error being generated, which will note the column that has the problem.

Ensure the fields named in the table adapter query match those in the query you have defined. The DAL does not seem to like mismatches. This will typically happen to your sprocs and queries after you add a new field to a table.
If you have changed the length of a varchar field in the database and the XML contained in the XSS file has not picked it up, find the field name and attribute definition in the XML and change it manually.
Remove primary keys from select lists in table adapters if they are not related to the data being returned.
Run your query in SQL Management Studio and ensure there are not duplicate records being returned. Duplicate records can generate duplicate primary keys which will cause this error.
SQL unions can spell trouble. I modified one table adapter by adding a ‘please select an employee’ record preceding the others. For the other fields I provided dummy data including, for example, strings of length one. The DAL inferred the schema from that initial record. Records following with strings of length 12 failed.

This worked for me, source: here
I had this error and it wasn't related with the DB constrains (at least in my case). I have an .xsd file with a GetRecord query that returns a group of records. One of the columns of that table was "nvarchar(512)" and in the middle of the project I needed to changed it to "nvarchar(MAX)".
Everything worked fine until the user entered more than 512 on that field and we begin to get the famous error message "Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints."
Solution: Check all the MaxLength property of the columns in your DataTable.
The column that I changed from "nvarchar(512)" to "nvarchar(MAX)" still had the 512 value on the MaxLength property so I changed to "-1" and it works!!.

The problem is with the Data Access designer. In Visual Studio, When we pull a View from "Server Explorer" to the Designer window, it is adding either a Primary key on a column randomly or marking something to a NOT NULL though it is actually set to null. Though the actual View creation in the SQL db server, doesn't have any primary key defined or the NOT NULL defined, the VS designer is adding this Key/constraint.
You can see this in the designer - it is shown with a key icon on left of the column name.
Solution: Right click on the key icon and select 'Delete Key'. This should solve the problem. You can also right click on a column and select "Properties" to see the list of properties of a column in the VS Data access designer and change the values appropriately.

This error was also showing in my project. I tried all the proposed solutions posted here, but no luck at all because the problem had nothing to do with fields size, table key fields definition, constraints or the EnforceConstraints dataset variable.
In my case I also have a .xsd object which I put there during the project design time (the Data Access Layer). As you drag your database table objects into the Dataset visual item, it reads each table definition from the underlying database and copies the constraints into the Dataset object exactly as you defined them when you created the tables in your database (SQL Server 2008 R2 in my case). This means that every table column created with the constraint of "not null" or "foreign key" must also be present in the result of your SQL statement or stored procedure.
After I included all the key columns and the columns defined as "not null" into my queries the problem disappeared completely.

Mine started working when I set AllowDBNull to True on a date field on a data table in the xsd file.

It sounds like possibly one or more of the columns being selected with:
e.eval, e.batch_no, e.crsnum, e.lect_code, e.prof_course
has AllowDBNull set to False in your Dataset defintion.

It is not clear why running a SELECT statement should involve enabling constraints. I don't know C# or related technologies, but I do know Informix database. There is something odd going on with the system if your querying code is enabling (and presumably also disabling) constraints.
You should also avoid the old-fashioned, non-standard Informix OUTER join notation. Unless you are using an impossibly old version of Informix, you should be using the SQL-92 style of joins.
Your question seems to mention two outer joins, but you only show one in the example query. That, too, is a bit puzzling.
The joining conditions between 'e' and the rest of the tables is:
AND c.crsnum = e.crsnum
AND c.batch_no = e.batch_no
AND d.lect_code= e.lect_code
This is an unusual combination. Since we do not have the relevant subset of the schema with the relevant referential integrity constraints, it is hard to know whether this is correct or not, but it is a little unusual to join between 3 tables like that.
None of this is a definitive answer to you problem; however, it may provide some guidance.

Thank you for all the input made so far. I just wanna add on that while one may have successfully normalized DB, updated any schema changes to their application (e.g. to dataset) or so, there is also another cause: sql CARTESIAN product (when joining tables in queries).
The existence of a cartesian query result will cause duplicate records in the primary (or key first) table of two or more tables being joined.
Even if you specify a "Where" clause in the SQL, a Cartesian may still occur if JOIN with secondary table for example contains the unequal join (useful when to get data from 2 or more UNrelated tables):
FROM tbFirst INNER JOIN
tbSystem ON tbFirst.reference_str <> tbSystem.systemKey_str
Solution for this:
tables should be related.
Thanks. chagbert

I solved the same problem by changing this from false to true. in the end I went into the database and changed my bit field to allow null, and then refreshed my xsd, and refreshed my wsdl and reference.cs and now all is well.
this.columnAttachPDFToEmailFlag.AllowDBNull = true;

Short and easy Soloution:
Go to MSSQL Studio Sever ;
Run the query of the cause of this error : in my case i see that id value was null because i forget to set Identity specification increment by 1.
So entered 1 for the id field as its is autoincremane and modify dont allow NULLS in desing view
That was the error that caused my bindingsource and tabel adapter throwin error at this code:
this.exchangeCheckoutReportTableAdapter.Fill(this.sbmsDataSet.ExchangeCheckouReportTable);

DirectCast(dt.Rows(0),DataRow).RowError
This directly gives the error

If you are using visual studio dataset designer to get the data table, and it is throwing an error 'Failed to Enable constraints'. I've faced the same problem, try to preview the data from the dataset designer itself and match it with table inside your database.
The best way to solve this issue is to delete the table adapter and create a new one instead.

* Secondary way : *
If you don't need [id] to be as Primary key,
Remove its primary key attribute:
on your DataSet > TableAdapter > right click on [id] column > select Delete key ...
Problem will be fixed.

I also had this issue and it was resolved after modifying the *.xsd to reflect the revised size of the column changed in the underlying SQL server.

To fix this error, i took off the troubling table adapter from the Dataset designer, and saved the dataset, and then dragged a fresh copy of the table adapter from the server explorer and that fixed it

I resolved this problem by opening the .xsd file with an XML reader and deleting a constraint placed on one of my views. For whatever reason when I added the view to the data it added a primary key constraint to one of the columns when there shouldn't have been one.
The other way is to open the .xsd file normally, look at the table/view causing the issue and delete any keys (right click column, select delete key) that should not be there.

Just want to add another possible reason for the exception to those listed above (especially for people who like to define dataset schema manually):
when in your dataset you have two tables and there is a relationship (DataSet.Reletions.Add()) defined from first table's field (chfield) to the second table's field (pfield), there is like an implicit constraint is added to that field to be unique even though it may be not specified as such explicitly in your definition neither as unique nor as a primary key.
As a consequence, should you have rows with repetitive values in that parent field (pfield) you'll get this exception too.

In my case this error was provoked by a size of a string column. What was weird was when I executed the exact same query in different tool, repeated values nor null values weren't there.
Then I discovered that the size of a string column size was 50 so when I called the fill method the value was chopped, throwing this exception.
I click on the column and set in the properties the size to 200 and the error was gone.
Hope this help

I solved this problem by doing the "subselect" like it:
string newQuery = "select * from (" + query + ") as temp";
When do it on mysql, all collunms properties (unique, non-null ...) will be cleared.

using (var tbl = new DataTable())
using (var rdr = cmd.ExecuteReader())
{
tbl.BeginLoadData();
try
{
tbl.Load(rdr);
}
catch (ConstraintException ex)
{
rdr.Close();
tbl.Clear();
// clear constraints, source of exceptions
// note: column schema already loaded!
tbl.Constraints.Clear();
tbl.Load(cmd.ExecuteReader());
}
finally
{
tbl.EndLoadData();
}
}

I received the same error type and in my case it solved it by removing the select fields and replacing them with a *. No idea why it was happening. The query had no typos or anything fancy.
Not the best solution but nothing else worked and I was getting exhausted.
In my search for a clear answer I found this on this:
https://www.codeproject.com/questions/45516/failed-to-enable-constraints-one-or-more-rows-cont
Solution 8
This error was also showing in my project, using Visual Studio 2010. I tried other solutions posted in other blogs, but no luck at all because the problem had nothing to do with fields size, table key fields definition, constraints or the EnforceConstraints dataset variable.
In my case I have a .xsd object which I put there during the project design time (in the Data Access Layer). As you drag your database table objects into the Dataset visual item, it reads each table definition from the underlying database and copies the constraints into the Dataset object exactly as you defined them when you created the tables in your database (SQL Server 2008 R2 in my case). This means that every table column created with the constraint of "not null" or "foreign key" must also be present in the result of your SQL statement or stored procedure.
After I included all the constrained columns (not null, primary key, foreign key, etc) into my queries the problem disappeared completely.
Perhaps you don't need all the table columns to be present in the query/stored procedure result, but because the constraints are still applied the error is shown if some constrained column does not appear in the result.
Hope this helps someone else.

If you have failing DataSet (not DataTable):
if (dataSet.HasErrors)
foreach (DataTable table in dataSet.Tables)
if (table.HasErrors)
foreach (var row in table.GetErrors())
Debug.Write($"Error in DataTable {table.TableName}: {row.RowError}")

if _sample_DataSet was the name of dataset that encounter error while filling, you can put the fill dataset inside a Try Catch and then put following code in catch{} block then you are able to exactly find the erroneous column.
foreach (DataTable _dtable in _sample_DataSet.DataSet.Tables)
{
foreach (DataRow dr in _dtable.Rows)
{
if (dr.HasErrors)
{
if (dr.HasErrors)
{
Debug.Write("Row error="+dr.RowError);
}
}
}

Add Unique Key For Nullable Columns - SQL Server

I'm using sql server 2008 R2 and would like to apply unique key constraint to nullable columns. This code works good, but if I have multiple columns to add this rule to, it would generate as many 'nullbuster' columns.
ALTER TABLE tblBranch
ADD nullbuster AS (CASE WHEN column1 IS NULL THEN BranchID ELSE NULL END);
CREATE UNIQUE INDEX UK_Column1 ON tblBranch(column1,nullbuster);
Is there any way that I could achieve the goal without generating new columns.
EDIT:
Followed #marc_s suggestion, here to create an unique key constraint.
The target column is BranchCode. Now, there is one record in the table that has NULL for BranchCode. When I try to insert a new record, with Null BranchCode, from c#, it gives an error saying - Cannot insert duplicate key for unique index UK_BranchCode.
But, when I manually insert a record in the database, it does accept null values.
Where am I going wrong.
CS
Guid gId = Guid.NewGuid();
cmd = new sqlcommand("insert into tblBranch(BranchId,BranchCode)
values(#BranchId,#BranchCode)",con);
cmd.Parameters.AddWithValue("#BranchId",gId);
cmd.Parameters.AddWithValue("#BranchCode",txtBranchCode.Text);//empty text here
con.Open();
cmd.ExecuteNonQuery();
cmd.Close();

So you're creating a nullbuster column for each nullable column you want to index? Seems like overkill....
Wouldn't it be much easier to just create filtered indexes for those nullable columns, something like:
CREATE UNIQUE INDEX UK_Column1 ON tblBranch(column1) WHERE column1 IS NOT NULL;
and thus allow any number of NULL entries, while uniquely indexing the other values. That way, you don't need to add all those nullbuster columns just to make indexing possible...
Read more about filtered indexes:
Create Filtered Indexes (on Technet)
Introduction to Filtered Index – Improve performance with Filtered Index
Update: in order to set a parameter to NULL (and not an empty string), use this code:
if(string.IsNullOrEmpty(txtBranchCode.Text))
{
cmd.Parameters.AddWithValue("#BranchCode", DBNull.Value);
}
else
{
cmd.Parameters.AddWithValue("#BranchCode", txtBranchCode.Text);
}

Use the filtered index suggestion provided by marc_s. You say that you are still getting a unique index violation. What does that tell you? It tells you you are inserting a duplicate key with regards to the index definition. You think, you aren't, but you definitely are.
How to debug that? You look at what you are inserting. You look at gId and txtBranchCode.Text in the debugger. Also, you look at the error message, because it says:
The duplicate key value is ...
All of these clues lead you to find that txtBranchCode.Text is not null, but an empty string. Insert NULL instead.

I suggest you move column1 to a new table and make it unique and non-nullable. Reference the Branch table using a foreign key in the new table. Populate the new table only where you have a (non-null) value for column1.
Creating a new table is the surest way to support any dependencies on column1. A column that permits nulls is not a key column but column1 apparently should be. Putting that column into a new table also happens to be the only way to satisfy Normal Form and that ought to be the default approach unless you have a very compelling reason to "denormalise" column1 into the Branch table where it doesn't seem to belong.

LINQ to SQL: Invalid column name 'DepartureGate', even though the column exists

I absolutely do not get this. The column exists in the table, I've ensured that the application is executing the query against the proper table in the proper database, and it still reports that it's an invalid column name.
I'm running NET 4.0, SQL Server 2008 Express Edition. Does anyone have any similar experience?
Executing queries against any other column name in the same table in the same database works extremely excellently. I added this column today and for some reason my application refuses to acknowledge the existence of this column.
Relevant column definition:
Relevant code:
(from x in flightDataContext.FlightDatas
where x.FlightDataId == FlightDataID && x.Departure == true
select new
{
x.ArrivalStationCode,
x.ArrivalStationName,
x.DepartureTime,
x.DepartureGate
}).SingleOrDefault();

I also faced the same problem.You can try the following solutions.
You should update your classes after the database changed(drag and drop your tables to the linq to sql file), so that the column is accessible with object name. if still problem exists then
the value you are saving in the coloumn is greater then the size specified for the coloumn. try varchar(MAX) if your coloumn is of varchar type.

When I encountered this error, I discovered that I had some spurious [Key] attributes on one of my Model objects that wasn't actually part of the unique key definition for that object's table. They had been innocuously sitting there until I refactored another of the object's relationships. Once I removed them, the error about the columns being invalid vanished.

Try this. Before this , delete the table and drag drog the table again on the DBML file and save the DBML.
var flight= flightDataContext.FlightDatas.SingleOrDefault(x=>x.FlightDataId == FlightDataID && x.Departure);
Now you can access:
flight.ArrivalStationCode,
flight.ArrivalStationName,
flight.DepartureTime,
flight.DepartureGate

Why does MS Access 2007 not allow a row insert, but then allow it on the next insert attempt?

My insert statement is:
INSERT INTO myTable (inst_id,user_id,app_id,type,accessed_on)
VALUES (3264,2580,'MyApp','Renew',Now);
...where all of the values are formatted correctly. The table has the above fields and one other, a long int auto-increment key field. The foreign keys are 'inst_id', 'user_id', and 'app_id'.
I am getting this error from Access:
...and the following error from VS 2005 when it errors out:
System.Data.OleDb.OleDbException: The changes you requested to the table
were not successful because they would
create duplicate values in the index,
primary key, or relationship. Change
the data in the field or fields that
contain duplicate data, remove the
index, or redefine the index to permit
duplicate entries and try again.
When making this insert query I can look into the database and see that the each of the foreign key values exist in their respective tables and have been for months (for the particular example I am using). These fields are also set so that I can have duplicates, so that is not the issue. Calls of this nature in other tables works great. I do not need to supply the auto-increment key value in the insert query, it adds it for me automatically (like it should).
The weird thing is that if I do this in my code:
try
{
//Execute the query here...
}
catch
{
//Execute the same query again
}
...or if I just try and execute this within Access twice, it works.
Has anyone encountered this before? Again, this type of insert works for other tables, all foreign keys are present in their respective tables, the primary key of this table is set as 'Auto-increment', and all fields (other than the primary key field of course) are set to allow duplicates.
Any ideas?
EDIT: Largest key before inserting: 343085. Largest key after inserting: 343086. The format is:
id: AutoNumber (Field Size=Long Interger, New Values=Increment, Indexed=Yes - No Duplicates)
inst_id: Number (Field Size=Long Interger, Required=Yes, Indexed=Yes - Duplicates OK)
user_id: Number (Field Size=Long Interger, Required=Yes, Indexed=Yes - Duplicates OK)
app_id: Text (Field Size=255, Required=Yes, Indexed=Yes - Duplicates OK)
type: Text (Field Size=50, Required=Yes, Indexed=No)
accessed_on: Date/Time (Default Value=Now(), Required=Yes, Indexed=No)

Going by some old memory here...
Try putting a timestamp field in your table.
I can't remember exactly why that works -- something to do with Access having difficulty identifying records / maybe some kind of locking or indexing quirk. I did some research on that several years ago when it happened to one of my tables.
The key violation the error refers to isn't a missing key in another table, it's a duplicate key in the same table. Sometimes, Access gets it's wires crossed and thinks that the key it's assigning to the new record is already assigned to another record in the table. I don't know what causes that to happen. But by putting a timestamp field in the table, it causes Access to think differently.
It's a frustrating fix, because I don't know why it works. And now I have an otherwise useless timestamp field in my table. But so be it.

MS-Access has been known to barf up spurious errors that have nothing to do with the problem they report. It wouldn't hurt to surround the column called "type" with brackets, [type].
http://office.microsoft.com/en-us/access-help/access-2007-reserved-words-and-symbols-HA010030643.aspx#_Toc272229038

Is the value Now changing between attempts so that there is now no longer a duplicate key error?

INSERT INTO myTable (inst_id,user_id,app_id,type,accessed_on)
VALUES (3264,2580,'MyApp','Renew',Now);
Can you just check this out with accessed_on datatype and Now datatype
Change the value type of DateTime to String while inserting that will be good.
Do let me know if this works for you.
Thanks
rAfee

I believe Jet/ACE will not understand the NOW() method.
And i worked with ACE version, the syntax could not work.
Need to find the other way for direct implementing the syntax.

I know long time ago I had a similuar issue. In my cases I was getting the same error but I didn't have any unique indexes in the table. I finally solved it by reparing and compacting the database.

C# MySqlCommand Multiple Drop Foreign Key problem

I'm hoping someone can help me with this problem.
I have a small app to 'patch' our DB as we need to augment the functionality and fix bugs. It reads in the patches which are just files with SQL statements and does some internal housekeeping, querying the DB and applying the patches that haven't been applied. Anyhow, this is the solution we have, good or bad, and it has worked pretty well... up until now.
I've found it necessary to drop the existing foreign key constraints on a number of tables and replace them with an ON DELETE CASCADE clause instead of the ON DELETE RESTRICT that they currently have. The idea being that the deletion of the PK on the table that theses other tables reference will result in the cleanup of all the others.
Essentially the patch file has the following in it:
ALTER TABLE `mydb`.`table2` DROP FOREIGN KEY `fk_table2_id`;
ALTER TABLE `mydb`.`table3` DROP FOREIGN KEY `fk_table3_id`;
ALTER TABLE `mydb`.`table4` DROP FOREIGN KEY `fk_table4_id`;
and the associated
ALTER TABLE `mydb`.`table2` ADD CONSTRAINT `fk_table2_id` FOREIGN KEY `fk_table_id` (`fk_the_id`) REFERENCES `mydb` (`id`)
ON DELETE CASCADE
ON UPDATE RESTRICT;
etc...
On the C# side, when I pass this string (the SQL statements found in the patch file) as follows:
MySqlCommand myCommand = new MySqlCommand(thePatch);
myCommand.Connection = connection;
myCommand.ExecuteNonQuery();
I get the following error message:
Error on rename of '.\mydb\table2' to '.\mydb#sql2-6a8-3f' (errno: 152)
I only get this when I've got two of these DROP FOREIGN KEY lines in the string.
I've made sure that the keys listed on the DROP lines are the keys and not the column names and everything else appears (to me at least) to be OK.
I've included mulitple SQL statements in a single MySqlCommand and had no problems, so I'm a bit frustrated.
I can take the same file and pipe it to mysql.exe from the command line and it works fine, so it seems like a difference in how the statements are handled.
Does anyone have any ideas on this one?
Thanks,
Matt

I don't know the full answer, but this may help troubleshoot a little deeper. When you alter a table MySQL uses the following steps:
CREATE TABLE newTableName with the new specifications
SELECT * FROM oldTableName INTO newTableName
Rename oldTableName to some intermediateTableName
rename newTableName to OldTableName
DROP TABLE intermediateTableName
The error you mention looks like it may be failing step 3 here. You might check file permissions. Beyond that, I will defer to those with greater knowledge about MySQL internals.