blocks|key|3159796|text|听起来可能有一个或多个列是用来选择的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3159797|+++e.eval,+e.batch_no,+e.crsnum,+e.lect_code,+e.prof_course|code-block|syntax|javascript|3159798|在数据集定义中将AllowDBNull设置为False。|3159799|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

It sounds like possibly one or more of the columns being selected with:

<pre><code> e.eval, e.batch_no, e.crsnum, e.lect_code, e.prof_course
</code></pre>

has AllowDBNull set to False in your Dataset defintion.

blocks|key|260158|text|此问题通常是由以下原因之一引起的|type|unstyled|depth|inlineStyleRanges|entityRanges|data|260159|为未设置为AllowDBNull|260160|duplicate的列返回不匹配的空值。|unordered-list-item|260161|
|260162|数据库和dataset|260163|
之间的列定义(例如，字符字段的大小)不匹配。|260164|如果结果集不是太大，请尝试本机运行查询并查看结果。如果您已经消除了空值，那么我的猜测是主键列正在被复制。|260165|或者，要查看确切的错误，您可以手动将Try/Catch块添加到生成的代码中，然后在引发异常时中断：|260166|​|260167|📷|atomic|offset|length|260168|260169|然后在命令窗口中，对获取错误的表调用GetErrors方法。|style|CODE|260170|对于C#，命令为?+dataTable.GetErrors()|260171|对于VB，该命令为?+dataTable.GetErrors|260172|260173|260174|260175|这将向您显示有错误的所有数据行。您可以获取并查看其中每一个的RowError，它应该会告诉您无效的列以及问题。因此，要查看出错的第一个数据行的错误，命令是：|260176|?+dataTable.GetErrors(0).RowError|260177|或者在C#中应该是?+dataTable.GetErrors()[0].RowError|260178|260179|260180|260181|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/e8d213f1615c815765f8ed92af5a1b5b.png|imageAlt|1|https://ask.qcloudimg.com/http-save/yehe-900000/990bef51e62d5462fac59dd1d3e989f0.png|2|https://ask.qcloudimg.com/http-save/yehe-900000/e3d4870cff7043a705b8553b9d2f862e.png^0|0|0|0|0|0|0|0|0|0|0|1|0|0|0|I|9|0|8|N|0|9|L|0|0|0|1|1|0|0|U|8|0|0|X|0|9|Z|0|0|0|1|2|0|0^^$0|@$1|2|3|4|5|6|7|1V|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1W|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|1X|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|1Y|8|@]|9|@]|A|$]]|$1|I|3|J|5|F|7|1Z|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|20|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|21|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|22|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|23|8|@]|9|@]|A|$]]|$1|S|3|T|5|U|7|24|8|@]|9|@$V|25|W|26|1|27]]|A|$]]|$1|X|3|R|5|6|7|28|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|6|7|29|8|@$V|2A|W|2B|10|11]]|9|@]|A|$]]|$1|12|3|13|5|6|7|2C|8|@$V|2D|W|2E|10|11]]|9|@]|A|$]]|$1|14|3|15|5|6|7|2F|8|@$V|2G|W|2H|10|11]]|9|@]|A|$]]|$1|16|3|R|5|6|7|2I|8|@]|9|@]|A|$]]|$1|17|3|T|5|U|7|2J|8|@]|9|@$V|2K|W|2L|1|2M]]|A|$]]|$1|18|3|R|5|6|7|2N|8|@]|9|@]|A|$]]|$1|19|3|1A|5|6|7|2O|8|@$V|2P|W|2Q|10|11]]|9|@]|A|$]]|$1|1B|3|1C|5|6|7|2R|8|@$V|2S|W|2T|10|11]]|9|@]|A|$]]|$1|1D|3|1E|5|6|7|2U|8|@$V|2V|W|2W|10|11]]|9|@]|A|$]]|$1|1F|3|R|5|6|7|2X|8|@]|9|@]|A|$]]|$1|1G|3|T|5|U|7|2Y|8|@]|9|@$V|2Z|W|30|1|31]]|A|$]]|$1|1H|3|R|5|6|7|32|8|@]|9|@]|A|$]]|$1|1I|3|-4|5|6|7|33|8|@]|9|@]|A|$]]]|1J|$1K|$5|1L|1M|1N|A|$1O|1P|1Q|-4]]|1R|$5|1L|1M|1N|A|$1O|1S|1Q|-4]]|1T|$5|1L|1M|1N|A|$1O|1U|1Q|-4]]]]

This problem is usually caused by one of the following

<ul>
<li>null values being returned for columns not set to AllowDBNull</li>
<li>duplicate rows being returned with the same primary key.</li>
<li>a mismatch in column definition (e.g. size of char fields) between the database and the dataset</li>
</ul>

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:

<img src="https://i.stack.imgur.com/HQrHa.png" alt="enter image description here">

Then within the command window, call <code>GetErrors</code> method on the table getting the error. 
For C#, the command would be <code>? dataTable.GetErrors()</code> 
For VB, the command is <code>? dataTable.GetErrors</code>

<img src="https://i.stack.imgur.com/ekNb5.png" alt="enter image description here">

This will show you all datarows which have an error. You can get then look at the <code>RowError</code> 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: 
<code>? dataTable.GetErrors(0).RowError</code> 
or in C# it would be <code>? dataTable.GetErrors()[0].RowError</code>

<img src="https://i.stack.imgur.com/Ynmlf.png" alt="enter image description here">

blocks|key|2946000|text|尚不清楚为什么运行SELECT语句需要启用约束。我不了解C#或相关技术，但我了解Informix数据库。如果您的查询代码启用了(可能也禁用了)约束，那么系统就会发生一些奇怪的事情。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2946001|您还应该避免使用老式的、非标准的Informix外部联接表示法。除非您使用的是非常旧的Informix版本，否则应该使用SQL-92样式的连接。|2946002|您的问题似乎提到了两个外连接，但在示例查询中只显示了一个。这也有点令人费解。|2946003|'e‘和其他表的连接条件是：|offset|length|style|CODE|2946004|AND+c.crsnum+=+e.crsnum++
AND+c.batch_no+=+e.batch_no++
AND+d.lect_code=+e.lect_code+|code-block|syntax|javascript|2946005|这是一个不同寻常的组合。由于我们没有具有相关引用完整性约束的模式的相关子集，因此很难知道这是否正确，但像这样在3个表之间连接有点不寻常。|2946006|所有这些都不是您问题的确切答案；但是，它可能会提供一些指导。|2946007|entityMap^0|0|0|0|1|1|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Y|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|Z|8|@$H|10|I|11|J|K]]|9|@]|A|$]]|$1|L|3|M|5|N|7|12|8|@]|9|@]|A|$O|P]]|$1|Q|3|R|5|6|7|13|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|14|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|V|$]]

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 '<code>e</code>' and the rest of the tables is:

<pre><code>AND c.crsnum = e.crsnum 
AND c.batch_no = e.batch_no 
AND d.lect_code= e.lect_code 
</code></pre>

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.

blocks|key|261450|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|261451|确保表适配器查询中指定的字段与您定义的查询中的字段相匹配。DAL似乎不喜欢不匹配。向表中添加新字段后，sprocs和查询通常会发生这种情况。|unordered-list-item|261452|如果您在数据库中更改了varchar字段的长度，但XSS文件中包含的XML没有选取它，请在XML中找到字段名和属性定义，然后手动更改它。如果主键与返回的数据不相关，则|261453|将主键从表适配器的选择列表中删除。|261454|在SQL+Management+Studio中运行查询，并确保没有返回重复的记录。重复的记录可能会生成重复的主键，这将导致此错误。|261455|SQL联合可能会带来麻烦。我修改了一个表适配器，在其他表适配器前面添加了“请选择一个员工”记录。对于其他字段，我提供了虚拟数据，例如，长度为1的字符串。DAL从初始记录中推断出模式。长度为12的字符串后面的记录失败。|261456|261457|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|-4|4|5|6|O|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|P|7|@]|8|@]|9|$]]|$1|D|3|E|4|C|6|Q|7|@]|8|@]|9|$]]|$1|F|3|G|4|C|6|R|7|@]|8|@]|9|$]]|$1|H|3|I|4|C|6|S|7|@]|8|@]|9|$]]|$1|J|3|K|4|C|6|T|7|@]|8|@]|9|$]]|$1|L|3|-4|4|5|6|U|7|@]|8|@]|9|$]]|$1|M|3|-4|4|5|6|V|7|@]|8|@]|9|$]]]|N|$]]

<ul>
<li>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. </li>
<li>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. </li>
<li>Remove primary keys from select lists in table adapters if they are not related to the data being returned. </li>
<li>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. </li>
<li>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. </li>
</ul>

blocks|key|3160009|text|您可以禁用数据集上的约束。它将允许您识别坏数据并帮助解决问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3160010|例如：|3160011|dataset.TableA.Clear();
dataset.EnforceConstraints+=+false;
dataAdapter1.daTableA.Fill(dataset,+TableA");|code-block|syntax|javascript|3160012|对于您来说，fill方法可能略有不同。|3160013|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

You can disable the constraints on the dataset. It will allow you to identify bad data and help resolve the issue.

e.g. 

<pre><code>dataset.TableA.Clear();
dataset.EnforceConstraints = false;
dataAdapter1.daTableA.Fill(dataset, TableA");
</code></pre>

The fill method might be slightly different for you.

blocks|key|256194|text|DirectCast(dt.Rows(0)，DataRow).RowError|type|unstyled|depth|inlineStyleRanges|entityRanges|data|256195|这将直接产生错误|256196|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

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

This directly gives the error

blocks|key|3160056|text|这个错误也出现在我的项目中。我尝试了这里发布的所有建议的解决方案，但都没有成功，因为问题与字段大小、表键字段定义、约束或EnforceConstraints数据集变量无关。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3160057|在我的例子中，我还有一个.xsd对象，它是我在项目设计时放在那里的(数据访问层)。当您将数据库表对象拖动到Dataset可视项中时，它将从基础数据库中读取每个表定义，并将约束复制到Dataset对象中，与您在数据库中创建表时定义的约束完全相同(在我的示例中为SQL+Server2008+R2+)。这意味着使用"not+null“或"foreign+key”约束创建的每个表列也必须出现在SQL语句或存储过程的结果中。|3160058|在我的查询中包含了所有键列和定义为"not+null“的列之后，这个问题就完全消失了。|3160059|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

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.

blocks|key|2946171|text|这对我很有效，来源：here|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2946172|我遇到了这个错误，而且它与DB约束无关(至少在我的例子中是这样)。我有一个带有GetRecord查询的.xsd文件，该查询返回一组记录。该表的其中一列是"nvarchar(512)“，在项目中间，我需要将其更改为"nvarchar(MAX)”。|2946173|一切都很正常，直到用户在该字段中输入的值超过512，并且我们开始收到著名的错误消息“未能启用约束。一行或多行包含违反非空、唯一或外键约束的值。”|2946174|解决方案:检查DataTable中列的所有MaxLength属性。|2946175|我从"nvarchar(+512+)“更改为"nvarchar(MAX)”的列在MaxLength属性上仍然具有512值，因此我更改为"-1“，并且它起作用了！！。|2946176|entityMap|0|LINK|mutability|MUTABLE|url|http://social.msdn.microsoft.com/Forums/en-US/Vsexpressvb/thread/27aec612-5ca4-41ba-80d6-0204893fdcd1/^0|A|4|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|D|3|E|5|6|7|X|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|Y|8|@]|9|@]|C|$]]|$1|H|3|I|5|6|7|Z|8|@]|9|@]|C|$]]|$1|J|3|K|5|6|7|10|8|@]|9|@]|C|$]]|$1|L|3|-4|5|6|7|11|8|@]|9|@]|C|$]]]|M|$N|$5|O|P|Q|C|$R|S]]]]

This worked for me, source: <a href="http://social.msdn.microsoft.com/Forums/en-US/Vsexpressvb/thread/27aec612-5ca4-41ba-80d6-0204893fdcd1/" rel="noreferrer">here</a>

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!!.

blocks|key|258413|text|这将查找表中有错误的所有行，打印出该行的主键和该行上发生的错误……|type|unstyled|depth|inlineStyleRanges|entityRanges|data|258414|这是在C#中实现的，但将其转换为VB应该不难。|258415|+foreach+(DataRow+dr+in+dataTable)
+{
+++if+(dr.HasErrors)
+++++{
++++++++Debug.Write("Row+");
++++++++foreach+(DataColumn+dc+in+dataTable.PKColumns)
++++++++++Debug.Write(dc.ColumnName+%2B+":+'"+%2B+dr.ItemArray[dc.Ordinal]+%2B+"',+");
++++++++Debug.WriteLine("+has+error:+"+%2B+dr.RowError);
+++++}
++}|code-block|syntax|javascript|258416|哦，对不起，PKColumns是我在扩展DataTable时添加的，它告诉我组成DataTable主键的所有列。如果您知道datatable中的主键列，则可以在此处遍历它们。在我的例子中，因为我的所有数据表都知道它们的PK列，所以我可以为所有的表自动编写这些错误的debug。|258417|输出如下所示：|258418|Row+FIRST_NAME:+'HOMER',+LAST_NAME:+'SIMPSON',+MIDDLE_NAME:+'J',++has+error:+Column+'HAIR_COLOR'+does+not+allow+DBNull.Value.|258419|如果您对上面的PKColumns部分感到困惑-这会打印出列名和值，这并不是必需的，但会添加有用的故障排除信息，以确定哪些列值可能会导致问题。删除此部分并保留其余部分仍将打印生成的SQLite错误，它将指出有问题的列。|258420|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|F|7|X|8|@]|9|@]|A|$G|H]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

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.
<pre><code> foreach (DataRow dr in dataTable)
 {
 if (dr.HasErrors)
 {
 Debug.Write(&quot;Row &quot;);
 foreach (DataColumn dc in dataTable.PKColumns)
 Debug.Write(dc.ColumnName + &quot;: '&quot; + dr.ItemArray[dc.Ordinal] + &quot;', &quot;);
 Debug.WriteLine(&quot; has error: &quot; + dr.RowError);
 }
 }
</code></pre>
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:
<pre><code>Row FIRST_NAME: 'HOMER', LAST_NAME: 'SIMPSON', MIDDLE_NAME: 'J', has error: Column 'HAIR_COLOR' does not allow DBNull.Value.
</code></pre>
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.

blocks|key|256294|text|如果您正在使用visual+studio数据集设计器获取数据表，并且它引发了错误“未能启用约束”。我也遇到过同样的问题，试着从数据集设计器本身预览数据，并将其与数据库中的表进行匹配。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|256295|解决此问题的最好方法是删除表适配器并创建一个新的表适配器。|256296|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

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.

blocks|key|2946254|text|感谢您到目前为止所做的所有输入。我只想补充一点，虽然一个人可能已经成功地规范化了数据库，更新了应用程序的任何模式更改(例如，对dataset)，但还有另一个原因:+sql笛卡尔产品(在查询中连接表时)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2946255|笛卡尔查询结果的存在将导致正在连接的两个或多个表的主表(或键优先)中存在重复记录。即使您在SQL中指定了"Where“子句，例如，如果与辅表的连接包含不等连接(在从2个或更多UNrelated表获取数据时很有用)，仍然可能出现笛卡尔连接：|2946256|来自tbFirst.reference_str+<>+tbSystem.systemKey_str上的tbFirst内部联接tbSystem的|2946257|blockquote|2946258|2946259|2946260|解决方案:表应该是相关的。|2946261|谢谢。查格伯特|2946262|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Q|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|A|$]]|$1|F|3|-4|5|G|7|S|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|T|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|U|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|V|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|W|8|@]|9|@]|A|$]]|$1|N|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|O|$]]

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):

<blockquote>
 FROM tbFirst INNER JOIN
 tbSystem ON tbFirst.reference_str &lt;> tbSystem.systemKey_str
</blockquote>

Solution for this:
 tables should be related.

Thanks. chagbert

blocks|key|2946273|text|*次要方式：*|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|2946274|2946275|如果不需要id作为主键，|2946276|删除其主键属性：|2946277|在您的DataSet+>+TableAdapter+>右键单击id列>选择Delete+key+...|2946278|问题将会得到解决。|2946279|entityMap^0|0|7|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|T|8|@]|D|@]|E|$]]|$1|G|3|H|5|6|7|U|8|@]|D|@]|E|$]]|$1|I|3|J|5|6|7|V|8|@]|D|@]|E|$]]|$1|K|3|L|5|6|7|W|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|X|8|@]|D|@]|E|$]]|$1|O|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|P|$]]

* Secondary way : *

<hr>

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.

blocks|key|258466|text|我也遇到过这个问题，在修改了*.xsd以反映底层SQL+server中修改后的列大小后，这个问题得到了解决。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|258467|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

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.

blocks|key|261588|text|我解决了同样的问题，把它从false改为true。最后，我进入数据库并将我的位字段更改为允许空，然后刷新我的xsd，并刷新我的wsdl和reference.cs，现在一切正常。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|261589|this.columnAttachPDFToEmailFlag.AllowDBNull+=+true;|code-block|syntax|javascript|261590|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

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.

<pre><code>this.columnAttachPDFToEmailFlag.AllowDBNull = true;
</code></pre>

blocks|key|3160266|text|通过使用XML读取器打开.xsd文件并删除放置在我的一个视图上的约束，我解决了这个问题。无论出于什么原因，当我将视图添加到数据中时，它会向其中一列添加一个主键约束，而这个约束本不应该存在。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3160267|另一种方法是正常打开.xsd文件，查看导致问题的表/视图，然后删除任何不应该存在的键(右键单击列，选择delete+key)。|offset|length|style|CODE|3160268|entityMap^0|0|1F|A|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

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 <code>delete key</code>) that should not be there.

blocks|key|261601|text|若要修复此错误，我从数据集设计器中移除了有问题的表适配器，并保存了数据集，然后从服务器资源管理器中拖动了表适配器的新副本并对其进行了修复。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|261602|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

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

blocks|key|2946371|text|我只想为上面列出的异常添加另一个可能的原因(特别是对于喜欢手动定义dataset模式的人)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2946372|如果在dataset中有两个表，并且定义了从第一个表的字段(chfield)到第二个表的字段(pfield)的关系(DataSet.Reletions.Add())，则类似于向该字段添加了一个隐式约束，使其成为唯一的唯一键()，即使在您的定义中可能没有显式地将其指定为唯一键或主键。|offset|length|style|CODE|2946373|因此，如果父字段(pfield)中有重复值的行，也会出现此异常。|2946374|entityMap^0|0|U|7|1B|6|1M|N|0|9|6|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@$D|N|E|O|F|G]|$D|P|E|Q|F|G]|$D|R|E|S|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|T|8|@$D|U|E|V|F|G]]|9|@]|A|$]]|$1|J|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|K|$]]

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 (<code>DataSet.Reletions.Add()</code>) defined from first table's field (<code>chfield</code>) to the second table's field (<code>pfield</code>), 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 (<code>pfield</code>) you'll get this exception too.

blocks|key|2946383|text|当我在xsd文件中数据表的日期字段上将AllowDBNull设置为True时，我的方法开始工作。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2946384|entityMap^0|J|B|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

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

blocks|key|3160372|text|在我的例子中，这个错误是由字符串列的大小引起的。奇怪的是，当我在不同的工具中执行完全相同的查询时，既没有重复值，也没有空值。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3160373|然后我发现字符串列的大小是50，所以当我调用fill方法时，这个值被截断了，抛出了这个异常。|3160374|我单击该列，并在属性中将size设置为200，错误就消失了。|3160375|希望这对你有所帮助|3160376|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|L|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|M|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

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

blocks|key|261639|text|问题出在数据访问设计器上。在Visual+Studio中，当我们将一个视图从“服务器资源管理器”拖到设计器窗口中时，它要么在列上随机添加一个主键，要么将一些内容标记为非空值，尽管它实际上被设置为null。虽然SQL+db服务器中的实际视图创建没有定义任何主键或非空值，但VS设计器正在添加此键/约束。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|261640|您可以在设计器中看到这一点-它在列名的左侧显示一个键图标。|261641|解决方案:右击按键图标并选择“删除按键”。这应该可以解决问题。您还可以右键单击列并选择"+properties“，以在VS数据访问设计器中查看列的属性列表，并相应地更改这些值。|261642|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

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.

blocks|key|261644|text|我通过像这样做"subselect“解决了这个问题：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|261645|string+newQuery+=+"select+*+from+("+%2B+query+%2B+")+as+temp";|code-block|syntax|javascript|261646|在mysql上执行此操作时，所有collunms属性(唯一、非空...)将被清除。|261647|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I solved this problem by doing the "subselect" like it:

<pre><code>string newQuery = "select * from (" + query + ") as temp";
</code></pre>

When do it on mysql, all collunms properties (unique, non-null ...) will be cleared.

blocks|key|260410|text|++++++++++++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();
++++++++++++++++}
++++++++++++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|260411|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code> 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();
 }
 }
</code></pre>

blocks|key|3160448|text|我收到了相同的错误类型，在我的例子中，它通过删除选择字段并将它们替换为*来解决它。不知道为什么会这样。查询没有输入错误或任何花哨的东西。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3160449|这不是最好的解决方案，但其他方法都不起作用，我感到精疲力尽。|3160450|在我寻找一个明确的答案的过程中，我发现了这个：https://www.codeproject.com/questions/45516/failed-to-enable-constraints-one-or-more-rows-cont|offset|length|3160451|解决方案8|style|BOLD|3160452|这个错误也出现在我的项目中，使用的是Visual+Studio+2010。我尝试了在其他博客上发布的其他解决方案，但一点也不走运，因为问题与字段大小、表键字段定义、约束或EnforceConstraints数据集变量无关。|CODE|3160453|在我的例子中，我有一个.xsd对象，它是我在项目设计时(在数据访问层)放在那里的。当您将数据库表对象拖动到Dataset可视项中时，它将从基础数据库中读取每个表定义，并将约束复制到Dataset对象中，与您在数据库(在我的示例中为SQL+Server2008+R2+)中创建表时定义的约束完全相同。这意味着使用"not+null“或"foreign+key”约束创建的每个表列也必须出现在SQL语句或存储过程的结果中。|3160454|在我的查询中包含了所有受约束的列(非null、主键、外键等)之后，这个问题就完全消失了。|3160455|也许您不需要所有的表列都出现在查询/存储过程结果中，但是因为仍然应用了约束，所以如果一些受约束的列没有出现在结果中，就会显示错误。|3160456|希望这对其他人有帮助。|3160457|entityMap|0|LINK|mutability|MUTABLE|url|https://www.codeproject.com/questions/45516/failed-to-enable-constraints-one-or-more-rows-cont^0|0|0|N|2M|0|0|0|5|0|2D|I|0|2I|7|0|0|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|15|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|16|8|@]|9|@$F|17|G|18|1|19]]|A|$]]|$1|H|3|I|5|6|7|1A|8|@$F|1B|G|1C|J|K]]|9|@]|A|$]]|$1|L|3|M|5|6|7|1D|8|@$F|1E|G|1F|J|N]]|9|@]|A|$]]|$1|O|3|P|5|6|7|1G|8|@$F|1H|G|1I|J|N]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1J|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1K|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|1L|8|@]|9|@]|A|$]]|$1|W|3|-4|5|6|7|1M|8|@]|9|@]|A|$]]]|X|$Y|$5|Z|10|11|A|$12|13]]]]

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:
 <a href="https://www.codeproject.com/questions/45516/failed-to-enable-constraints-one-or-more-rows-cont" rel="nofollow noreferrer">https://www.codeproject.com/questions/45516/failed-to-enable-constraints-one-or-more-rows-cont</a>

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 <code>EnforceConstraints</code> 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 <code>Dataset</code> 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.

blocks|key|3160509|text|简单易行的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3160510|转到MSSQL+Studio+Sever；|3160511|运行此错误原因的查询:在我的示例中，我看到id值为空，因为我忘记将标识规范增量设置为1。|offset|length|style|BOLD|3160512|​|3160513|📷|atomic|3160514|3160515|因此为id字段输入了1，因为它是自动递增和修改在设计视图中不允许空值|3160516|3160517|3160518|3160519|这就是导致我的bindingsource和tabel适配器在以下代码中抛出错误的错误：|3160520|+++this.exchangeCheckoutReportTableAdapter.Fill(this.sbmsDataSet.ExchangeCheckouReportTable);|code-block|syntax|javascript|3160521|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/1665b610ac559e98e6f0950ae65b9efe.png|imageAlt|1|https://ask.qcloudimg.com/http-save/yehe-900000/bb4a1cd1d8aa24b0eaca1096d3227e27.png^0|0|0|X|B|0|0|0|1|0|0|0|0|0|0|1|1|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1C|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1D|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|1E|8|@$F|1F|G|1G|H|I]]|9|@]|A|$]]|$1|J|3|K|5|6|7|1H|8|@]|9|@]|A|$]]|$1|L|3|M|5|N|7|1I|8|@]|9|@$F|1J|G|1K|1|1L]]|A|$]]|$1|O|3|K|5|6|7|1M|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|1N|8|@]|9|@]|A|$]]|$1|R|3|K|5|6|7|1O|8|@]|9|@]|A|$]]|$1|S|3|M|5|N|7|1P|8|@]|9|@$F|1Q|G|1R|1|1S]]|A|$]]|$1|T|3|K|5|6|7|1T|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|1U|8|@]|9|@]|A|$]]|$1|W|3|X|5|Y|7|1V|8|@]|9|@]|A|$Z|10]]|$1|11|3|-4|5|6|7|1W|8|@]|9|@]|A|$]]]|12|$13|$5|14|15|16|A|$17|18|19|-4]]|1A|$5|14|15|16|A|$17|1B|19|-4]]]]

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.

<a href="https://i.stack.imgur.com/KPmHf.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/KPmHf.png" alt="enter image description here"></a>

So entered 1 for the id field as its is autoincremane and modify dont allow NULLS in desing view

<a href="https://i.stack.imgur.com/5kal7.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5kal7.png" alt="enter image description here"></a>

That was the error that caused my bindingsource and tabel adapter throwin error at this code:

<pre><code> this.exchangeCheckoutReportTableAdapter.Fill(this.sbmsDataSet.ExchangeCheckouReportTable);
</code></pre>

I make an outer join and executed successfully in the <code>informix</code> database but I get the following exception in my code:

<pre><code>DataTable dt = TeachingLoadDAL.GetCoursesWithEvalState(i, bat);
</code></pre>

<blockquote>
 Failed to enable constraints. One or more rows contain values
 violating non-null, unique, or foreign-key constraints.
</blockquote>

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:

<pre><code> 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 = ....
</code></pre>

The problem happens with the table <code>cc1assiscrseval</code>. The primary key is (batch_no, crsnum, lect_code).

How to fix this problem?

<hr>

EDIT:

According to <code>@PaulStock</code> advice:
I do what he said, and i get:

<blockquote>
 ? dt.GetErrors()[0] {System.Data.DataRow} HasErrors: true ItemArray:
 {object[10]} RowError: "Column 'eval' does not allow DBNull.Value."
</blockquote>

So I solve my problem by replacing <code>e.eval</code> to ,<code>NVL (e.eval,'') eval</code>.and this solves my problem.
Thanks a lot.

Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints

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我执行了一个外部连接，并在informix数据库中成功执行，但我的代码中出现了以下异常：DataTable dt = TeachingLoadDAL.GetCoursesWithEvalState(i, bat);无法启用约束。一个或多个行包含违反非null、unique或外键约束的值。我知道问题所在，但我不知道如何解...

问无法启用约束。一个或多个行包含违反非null、unique或外键约束的值
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