如何知道CONSTRAINT_NAME是主鍵還是外鍵？

Question

使用SQL Server 2005

SELECT CONSTRAINT_NAME 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE TABLE_NAME = @TableName 
    AND COLUMN_NAME=@ColumnName 

這個SQL，我得到了主鍵和外鍵。

我怎樣才能得到外鍵？ 如何查看約束是主鍵還是外鍵？

感謝

Answer 1

我用下面的SQL與SQL Server 2005，以獲得通過主鍵約束名稱：

SELECT Constraint_Name 
FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS 
WHERE UNIQUE_CONSTRAINT_NAME = 
    (SELECT CONSTRAINT_NAME 
    FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
    WHERE TABLE_NAME = @TableName AND COLUMN_NAME = @ColumnName) 

要通過Foreing重點得到約束名稱：

SELECT CONSTRAINT_NAME 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE TABLE_NAME = @TableName AND COLUMN_NAME = @ColumnName 

爲了得到外鍵的表和字段的約束名稱：

SELECT TABLE_NAME, COLUMN_NAME 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE CONSTRAINT_NAME = @ConstraintName 

要獲取主鍵的表和字段由C onstraint名稱：

SELECT TABLE_NAME, COLUMN_NAME 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE CONSTRAINT_NAME = 
    (SELECT UNIQUE_CONSTRAINT_NAME 
    FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS 
    WHERE CONSTRAINT_NAME = @ConstraintName) 

Answer 2

這取決於你的DBMS，但是約束應該在目標表和列的地方。

如果是外鍵約束，目標表將與當前表不同。嘗試

select * 

，而不是

select constraint_name 

看到所有你能一起工作的神奇列。

Answer 3

SELECT CONSTRAINT_NAME 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE TABLE_NAME = @TableName 
    AND COLUMN_NAME=@ColumnName 
    AND REFERENCED_COLUMN_NAME IS NOT NULL 

Answer 4

這不是最優雅的解決方案，但MS SQL Server使用PK & FK前綴鍵命名約定，所以你可以使用類似...

SELECT CONSTRAINT_NAME 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE TABLE_NAME = @TableName 
AND LEFT(CONSTRAINT_NAME,2) = 'FK' 

如果這是你的DBMS :)

編輯

當我試圖通過Quassnoi的答案我有一個「無效列名稱「REFERENCED_COLUMN_NAME」。「錯誤。

Answer 5

找到一個更好的解決方案here

代碼下面添加的完整性，但都歸功於皮納爾戴夫

SELECT f.name AS ForeignKey, 
    OBJECT_NAME(f.parent_object_id) AS TableName, 
    COL_NAME(fc.parent_object_id, 
    fc.parent_column_id) AS ColumnName, 
    OBJECT_NAME (f.referenced_object_id) AS ReferenceTableName, 
    COL_NAME(fc.referenced_object_id, 
    fc.referenced_column_id) AS ReferenceColumnName 
FROM sys.foreign_keys AS f 
LEFT JOIN sys.foreign_key_columns AS fc 
    ON f.OBJECT_ID = fc.constraint_object_id 

如果你只是想在主鍵...

SELECT i.name AS IndexName, 
     OBJECT_NAME(ic.OBJECT_ID) AS TableName, 
     COL_NAME(ic.OBJECT_ID,ic.column_id) AS ColumnName 
FROM sys.indexes AS i 
     INNER JOIN sys.index_columns AS ic 
     ON i.OBJECT_ID = ic.OBJECT_ID 
    AND i.index_id = ic.index_id 
WHERE i.is_primary_key = 1 

添加此爲一個額外的答案，因爲它是從我以前的一個很遠:)

Answer 6

我使用類似的東西。它也適用於SQL Server 2000。

select object_name(fkx.constid) as fk_name, 
     fkx.keyno as num, 
     object_name(fkx.fkeyid) as child_table, 
     col_name(fkx.fkeyid, fkx.fkey) as child_column, 
     object_name(fkx.rkeyid) as parent_table, 
     col_name(fkx.rkeyid, fkx.rkey) as parent_column 
from sysforeignkeys fkx 
order by fk_name, fkx.keyno 

這一切都在系統表和視圖，這是很好的記錄。