Failed to enable constraints. One or more rows con

Question

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.

Answer 1

• 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.

Answer 2

DirectCast(dt.Rows(0),DataRow).RowError

This directly gives the error

Answer 3

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

Answer 4

            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();
                }
            }

Answer 5

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.

Answer 6

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.