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Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign
...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...
How to store arrays in MySQL?
I have two tables in MySQL. Table Person has the following columns:
7 Answers
7
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Is there a typical state machine implementation pattern?
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I prefer to use a table driven approach for most state machines:
typedef enum { STATE_INITIAL, STATE_FOO, STATE_BAR, NUM_STATES } state_t;
typedef struct instance_data instance_data_t;
typedef state_t state_func_t( instance_data_t *data );
s...
What is a stored procedure?
...ut the user will not need to have read/write permissions on the underlying tables. This is a good first step against SQL injection.
Stored procedures do come with downsides, basically the maintenance associated with your basic CRUD operation. Let's say for each table you have an Insert, Update, Del...
Why use multiple columns as primary keys (composite primary key)
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Another example of compound primary keys are the usage of Association tables. Suppose you have a person table that contains a set of people and a group table that contains a set of groups. Now you want to create a many to many relationship on person and group. Meaning each person can belong t...
What is the difference between a schema and a table and a database?
...bably a n00blike (or worse) question. But I've always viewed a schema as a table definition in a database. This is wrong or not entirely correct. I don't remember much from my database courses.
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Using Excel OleDb to get sheet names IN SHEET ORDER
...tring excelFile)
{
OleDbConnection objConn = null;
System.Data.DataTable dt = null;
try
{
// Connection String. Change the excel file to the file you
// will search.
String connString = "Provider=Microsoft.Jet.OLEDB.4.0;" +
"Data Source=" + excelFi...
Create code first, many to many, with additional fields in association table
... not possible to create a many-to-many relationship with a customized join table. In a many-to-many relationship EF manages the join table internally and hidden. It's a table without an Entity class in your model. To work with such a join table with additional properties you will have to create actu...
How to delete a column from a table in MySQL
Given the table created using:
8 Answers
8
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How to add column if not exists on PostgreSQL?
Question is simple. How to add column x to table y , but only when x column doesn't exist ? I found only solution here how to check if column exists.
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