nullable unique constraint ef
// Add unique nullable index
string indexName = "IX_UQ_UniqueColumn";
string tableName = "dbo.ExampleClasses";
string columnName = "UniqueColumn";
Sql(string.Format(@"
CREATE UNIQUE NONCLUSTERED INDEX {0}
ON {1}({2})
WHERE {2} IS NOT NULL;",
indexName, tableName, columnName));