Check if a SQL table exists

Question

What\'s the best way to check if a table exists in a Sql database in a database independant way?

I came up with:

   bool exists;
   const string sql         


        

Answer 1

The following works well for me...

private bool TableExists(SqlConnection conn, string database, string name)
{
    string strCmd = null;
    SqlCommand sqlCmd = null;

    try
    {
        strCmd = "select case when exists((select '['+SCHEMA_NAME(schema_id)+'].['+name+']' As name FROM [" + database + "].sys.tables WHERE name = '" + name + "')) then 1 else 0 end";
        sqlCmd = new SqlCommand(strCmd, conn);

        return (int)sqlCmd.ExecuteScalar() == 1;
    }
    catch { return false; }
}

Answer 2

If you're trying for database independence you will have to assume a minimum standard. IIRC The ANSI INFORMATION_SCHEMA views are required for ODBC conformance, so you could query against them like:

select count (*) 
  from information_schema.tables 
 where table_name = 'foobar'

Given that you are using ODBC, you can also use various ODBC API calls to retrieve this metadata as well.

Bear in mind that portability equates to write-once test anywhere so you are still going to have to test the application on every platform you intend to support. This means that you are inherently limited to a finite number of possible database platforms as you only have so much resource for testing.

The upshot is that you need to find a lowest common denominator for your application (which is quite a lot harder than it looks for SQL) or build a platform-dependent section where the non-portable functions can be plugged in on a per-platform basis.

Answer 3

bool exists;

try
{
    // ANSI SQL way.  Works in PostgreSQL, MSSQL, MySQL.  
    var cmd = new OdbcCommand(
      "select case when exists((select * from information_schema.tables where table_name = '" + tableName + "')) then 1 else 0 end");

    exists = (int)cmd.ExecuteScalar() == 1;
}
catch
{
    try
    {
        // Other RDBMS.  Graceful degradation
        exists = true;
        var cmdOthers = new OdbcCommand("select 1 from " + tableName + " where 1 = 0");
        cmdOthers.ExecuteNonQuery();
    }
    catch
    {
        exists = false;
    }
}

Answer 4

I would avoid executing the select count(x) from xxxxxx as the DBMS will actually go ahead and do it which may take some time for a large table.

Instead just prepare a select * from mysterytable query. The prepare will fail if mysterytable does not exist. There is no need to actually execute the prepared statement.

Answer 5

In current project on my job I need to write 'data agent' which would support a lot of database types.

So I decided to do next: write a base class with the base (database independent) functionality using virtual methods and override in subclasses all database-specific moments

Answer 6

Very Simple

use YOUR_DATABASE --OPTIONAL
SELECT count(*) as Exist from INFORMATION_SCHEMA.TABLES where table_name = 'YOUR_TABLE_NAME'

If the answer is 1, There is a table. If the answer is 0, There is no table.