如何獲取表和主鍵，如果表沒有主鍵，則顯示null？

Question

我目前正在嘗試通過在C＃中調用以下SQL來檢索每個表的表名和主鍵。 這是我到目前為止所嘗試的：

SELECT t.TABLE_NAME As 'Table Name',
       Keys.COLUMN_NAME AS 'Primary Key'
FROM INFORMATION_SCHEMA.TABLES t 
left outer join INFORMATION_SCHEMA.TABLE_CONSTRAINTS Constraints
         on  t.TABLE_NAME = Constraints.Table_name 
         and t.Table_Schema = Constraints.Table_Schema 
left outer join INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS Keys 
         ON  Constraints.TABLE_NAME = Keys.TABLE_NAME 
         and Constraints.CONSTRAINT_NAME = Keys.CONSTRAINT_NAME 
         and Constraints.CONSTRAINT_TYPE = 'PRIMARY KEY'

問題是，如果表沒有主鍵，我希望結果只包含一個“null”條目。 當它工作時，由於某種原因，結果包含“Salary”表的副本，如下所示。 Salary和Employees表都有主鍵，而“Test”表沒有：

編輯：我現在試過這個，它似乎工作。 這樣做有什么不利之處嗎？

SELECT T.TABLE_NAME As 'Table Name'
    ,       (
            Select K1.COLUMN_NAME
            From INFORMATION_SCHEMA.TABLE_CONSTRAINTS As C1
                Join INFORMATION_SCHEMA.KEY_COLUMN_USAGE As K1
                    On C1.TABLE_SCHEMA = K1.TABLE_SCHEMA
                        And C1.TABLE_NAME = K1.TABLE_NAME 
                        And C1.CONSTRAINT_NAME = K1.CONSTRAINT_NAME 
            Where C1.CONSTRAINT_TYPE = 'PRIMARY KEY'
                And T.TABLE_SCHEMA = C1.TABLE_SCHEMA 
                And T.TABLE_NAME = C1.TABLE_NAME 
            )As PrimaryKeyColumns
FROM INFORMATION_SCHEMA.TABLES As T 

Answer 1

嘗試替換此條件Constraints.CONSTRAINT_TYPE = 'PRIMARY KEY' ：

SELECT t.TABLE_NAME As 'Table Name',
       Keys.COLUMN_NAME AS 'Primary Key'
FROM INFORMATION_SCHEMA.TABLES t 
left outer join INFORMATION_SCHEMA.TABLE_CONSTRAINTS Constraints
         on  t.TABLE_NAME = Constraints.Table_name 
         and t.Table_Schema = Constraints.Table_Schema  
         and Constraints.CONSTRAINT_TYPE = 'PRIMARY KEY'       
left outer join INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS Keys 
         ON  Constraints.TABLE_NAME = Keys.TABLE_NAME 
         and Constraints.CONSTRAINT_NAME = Keys.CONSTRAINT_NAME 

Answer 2

您應該考慮具有多列的PK。 您可以通過更改為子查詢來執行此操作：

SELECT T.TABLE_NAME As 'Table Name'
    ,   Stuff(
            (
            Select ', ' + K1.COLUMN_NAME
            From INFORMATION_SCHEMA.TABLE_CONSTRAINTS As C1
                Join INFORMATION_SCHEMA.KEY_COLUMN_USAGE As K1
                    On C1.TABLE_SCHEMA = K1.TABLE_SCHEMA
                        And C1.TABLE_NAME = K1.TABLE_NAME 
                        And C1.CONSTRAINT_NAME = K1.CONSTRAINT_NAME 
            Where C1.CONSTRAINT_TYPE = 'PRIMARY KEY'
                And T.TABLE_SCHEMA = C1.TABLE_SCHEMA 
                And T.TABLE_NAME = C1.TABLE_NAME 
            For Xml Path(''), type
            ).value('.', 'nvarchar(max)')
            , 1, 2, '') As PrimaryKeyColumns
FROM INFORMATION_SCHEMA.TABLES As T 

---

順便說一句，如果你真的想在頁面視圖中使用連接，你需要嵌套連接。 問題是您有兩個外連接，外鍵中的列在輸出中生成行。 應該注意的是，與前面提到的子查詢方法相比，以下方法的缺點是，如果主鍵由多列組成，您將獲得多行。 也就是說，您可以在SQL Server中嵌套連接，以便它首先處理內部，內部連接，然后處理外部連接：

SELECT T.TABLE_NAME As 'Table Name'
    , Keys.COLUMN_NAME AS 'Primary Key'
FROM INFORMATION_SCHEMA.TABLES As T
    Left Join( INFORMATION_SCHEMA.TABLE_CONSTRAINTS Constraints
        Join INFORMATION_SCHEMA.KEY_COLUMN_USAGE As Keys 
            On  Constraints.TABLE_SCHEMA = Keys.TABLE_SCHEMA 
                And Constraints.TABLE_NAME = Keys.TABLE_NAME 
                And Constraints.CONSTRAINT_NAME = Keys.CONSTRAINT_NAME 
                And Constraints.CONSTRAINT_TYPE = 'PRIMARY KEY' )
        On T.TABLE_SCHEMA = Constraints.TABLE_SCHEMA 
            And T.TABLE_NAME = Constraints.TABLE_NAME 

在此查詢中，首先處理TABLE_CONSTRAINTS和KEY_COLUMN_USAGE之間的內部連接，並將結果組合在Left Join to TABLES視圖中。

Answer 3

我看到你已經接受了你的答案，但這是一個純粹的C＃答案，以防有人感興趣：

static void Main(string[] args)
{
    Server server = new Server("serverName");
    Database db = server.Databases["DatabaseName"];

    string tableName = "TableName";

    Table table = db.Tables[tableName];

    if (table != null)
    {
        Console.WriteLine("Table:  {0}", tableName);
        if (table.Columns.Count > 0)
        {
            Console.WriteLine("  Primary Key Columns:");
            foreach (Column column in table.Columns)
            {
                if (column.InPrimaryKey)
                {
                    Console.WriteLine(string.Format("    {0}", column.Name));
                }
            }
        }
        else
        {
            Console.WriteLine("  No primary key.", tableName);
        }
    }
    Console.WriteLine("Press ENTER to exit...");
    Console.ReadLine();
}

您將需要添加對Microsoft.SqlServer.Management.Sdk.Sfc和Microsoft.SqlServer.Smo程序集的引用，並導入相應的名稱空間。

Answer 4

select
  TABLE_SCHEMA, 
  TABLE_NAME 
from 
  INFORMATION_SCHEMA.TABLES
where 
  objectproperty(object_id(table_name),'TableHasPrimaryKey')=0
ORDER BY 
  TABLE_NAME